Convert.ChangeType Convert.ChangeType Convert.ChangeType Convert.ChangeType Method

Definice

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of a specified type whose value is equivalent to a specified object.

Přetížení

ChangeType(Object, Type) ChangeType(Object, Type) ChangeType(Object, Type) ChangeType(Object, Type)

Vrátí objekt zadaného typu a jehož hodnota je ekvivalentem zadaného objektu.Returns an object of the specified type and whose value is equivalent to the specified object.

ChangeType(Object, TypeCode) ChangeType(Object, TypeCode) ChangeType(Object, TypeCode)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object.

ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object. Parametr poskytuje informace o formátování specifické pro jazykovou verzi.A parameter supplies culture-specific formatting information.

ChangeType(Object, TypeCode, IFormatProvider) ChangeType(Object, TypeCode, IFormatProvider) ChangeType(Object, TypeCode, IFormatProvider)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object. Parametr poskytuje informace o formátování specifické pro jazykovou verzi.A parameter supplies culture-specific formatting information.

ChangeType(Object, Type) ChangeType(Object, Type) ChangeType(Object, Type) ChangeType(Object, Type)

Vrátí objekt zadaného typu a jehož hodnota je ekvivalentem zadaného objektu.Returns an object of the specified type and whose value is equivalent to the specified object.

public:
 static System::Object ^ ChangeType(System::Object ^ value, Type ^ conversionType);
public static object ChangeType (object value, Type conversionType);
static member ChangeType : obj * Type -> obj
Public Shared Function ChangeType (value As Object, conversionType As Type) As Object

Parametry

value
Object Object Object Object

Objekt, který implementuje IConvertible rozhraní.An object that implements the IConvertible interface.

conversionType
Type Type Type Type

Typ objektu, který chcete vrátit.The type of object to return.

Návraty

Objekt, jehož typ je conversionType a jehož hodnota je valueekvivalentní.An object whose type is conversionType and whose value is equivalent to value.

-nebo--or- Odkaz s hodnotou nullNothing (v Visual Basic), value Pokud null je conversionType a není hodnotovým typem.A null reference (Nothing in Visual Basic), if value is null and conversionType is not a value type.

Výjimky

Tento převod není podporován.This conversion is not supported.

-nebo--or- valueje null aconversionType je typ hodnoty.value is null and conversionType is a value type.

-nebo--or- valueneimplementuje IConvertible rozhraní.value does not implement the IConvertible interface.

valuenení ve formátu, který rozpozná conversionType.value is not in a format recognized by conversionType.

valuepředstavuje číslo, které je mimo rozsah conversionType.value represents a number that is out of the range of conversionType.

Příklady

Následující příklad ukazuje použití ChangeType metody.The following example illustrates the use of the ChangeType method.

using namespace System;

int main()
{
   Double d = -2.345;
   int i =  *safe_cast<Int32^>(Convert::ChangeType( d, int::typeid ));
   Console::WriteLine( "The double value {0} when converted to an int becomes {1}", d, i );
   String^ s = "12/12/98";
   DateTime dt =  *safe_cast<DateTime^>(Convert::ChangeType( s, DateTime::typeid ));
   Console::WriteLine( "The string value {0} when converted to a Date becomes {1}", s, dt );
}
using System;

public class ChangeTypeTest {
    public static void Main() {

        Double d = -2.345;
        int i = (int)Convert.ChangeType(d, typeof(int));

        Console.WriteLine("The double value {0} when converted to an int becomes {1}", d, i);

        string s = "12/12/98";
        DateTime dt = (DateTime)Convert.ChangeType(s, typeof(DateTime));

        Console.WriteLine("The string value {0} when converted to a Date becomes {1}", s, dt);        
    }
}
Public Class ChangeTypeTest
    
    Public Shared Sub Main()
        Dim d As [Double] = - 2.345
        Dim i As Integer = CInt(Convert.ChangeType(d, GetType(Integer)))
        
        Console.WriteLine("The double value {0} when converted to an int becomes {1}", d, i)
        Dim s As String = "12/12/98"
        Dim dt As DateTime = CType(Convert.ChangeType(s, GetType(DateTime)), DateTime)
        
        Console.WriteLine("The string value {0} when converted to a Date becomes {1}", s, dt)
    End Sub
End Class

Poznámky

ChangeTypeje metoda převodu pro obecné účely, která převádí objekt určený parametrem value na conversionType.ChangeType is a general-purpose conversion method that converts the object specified by value to conversionType. Parametr může být objekt libovolného typu a conversionType může také být Type objekt, který představuje libovolný základní nebo vlastní typ. valueThe value parameter can be an object of any type, and conversionType can also be a Type object that represents any base or custom type. Aby převod mohl být úspěšný, value musí IConvertible implementovat rozhraní, protože metoda jednoduše zabalí volání odpovídající IConvertible metody.For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. Metoda vyžaduje, aby byl převod value na conversionType , který je podporován.The method requires that conversion of value to conversionType be supported.

Tato metoda používá pro převod jazykovou verzi aktuálního vlákna.This method uses the current thread's culture for the conversion.

Poznámky pro volající

ChangeType(Object, Type) Metoda může převést hodnotu výčtu na jiný typ.The ChangeType(Object, Type) method can convert an enumeration value to another type. Nemůže však převést jiný typ na hodnotu výčtu, i když je typ zdroje základní typ výčtu.However, it cannot convert another type to an enumeration value, even if the source type is the underlying type of the enumeration. Chcete-li převést typ na hodnotu výčtu, použijte operátor přetypování (in C#) nebo funkci pro převod (v Visual Basic).To convert a type to an enumeration value, use a casting operator (in C#) or a conversion function (in Visual Basic). Následující příklad ukazuje převod na a z hodnoty výčtu kontinentu .The following example illustrates the conversion to and from a Continent enumeration value.

[!code-csharpSystem.Convert.ChangeType#5] [!code-vbSystem.Convert.ChangeType#5][!code-csharpSystem.Convert.ChangeType#5] [!code-vbSystem.Convert.ChangeType#5] ChangeType(Object, Type) Metoda může převést typ s povolenou hodnotou null na jiný typ.The ChangeType(Object, Type) method can convert a nullable type to another type. Nemůže však převést jiný typ na hodnotu typu s možnou hodnotou null, i když conversionType je základní typ. Nullable<T> Chcete-li provést převod, můžete použít operátor přetypování (v C#) nebo funkci konverze (v Visual Basic).However, it cannot convert another type to a value of a nullable type, even if conversionType is the underlying type of the Nullable<T>.To perform the conversion, you can use a casting operator (in C#) or a conversion function (in Visual Basic). Následující příklad ukazuje převod na typ a z typu s možnou hodnotou null.The following example illustrates the conversion to and from a nullable type.

[!code-csharpSystem.Convert.ChangeType#7] [!code-vbSystem.Convert.ChangeType#7][!code-csharpSystem.Convert.ChangeType#7] [!code-vbSystem.Convert.ChangeType#7]

ChangeType(Object, TypeCode) ChangeType(Object, TypeCode) ChangeType(Object, TypeCode)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object.

public:
 static System::Object ^ ChangeType(System::Object ^ value, TypeCode typeCode);
public static object ChangeType (object value, TypeCode typeCode);
static member ChangeType : obj * TypeCode -> obj

Parametry

value
Object Object Object Object

Objekt, který implementuje IConvertible rozhraní.An object that implements the IConvertible interface.

typeCode
TypeCode TypeCode TypeCode TypeCode

Typ objektu, který chcete vrátit.The type of object to return.

Návraty

Objekt, jehož nadřízený typ je typeCode a jehož hodnota je valueekvivalentní.An object whose underlying type is typeCode and whose value is equivalent to value.

-nebo--or- Odkaz s hodnotou nullNothing (v Visual Basic), value Pokud null je typeCode a Emptyje String, nebo Object.A null reference (Nothing in Visual Basic), if value is null and typeCode is Empty, String, or Object.

Výjimky

Tento převod není podporován.This conversion is not supported.

-nebo--or- valueje null atypeCode určuje typ hodnoty.value is null and typeCode specifies a value type.

-nebo--or- valueneimplementuje IConvertible rozhraní.value does not implement the IConvertible interface.

valuenení ve formátu rozpoznaném typeCode typem.value is not in a format recognized by the typeCode type.

valuepředstavuje číslo, které je mimo rozsah typeCode typu.value represents a number that is out of the range of the typeCode type.

Formát typeCode je neplatný.typeCode is invalid.

Příklady

Následující příklad ukazuje, jak použít ChangeType(Object, TypeCode) metodu ke Object změně typu na typ určený TypeCode parametrem, pokud je to možné.The following example illustrates how to use the ChangeType(Object, TypeCode) method to change an Object to the type specified by the TypeCode parameter, if possible.

using namespace System;

void main()
{
   Double d = -2.345;
   int i = (int) Convert::ChangeType(d, TypeCode::Int32);

   Console::WriteLine("The Double {0} when converted to an Int32 is {1}", d, i);

   String^ s = "12/12/2009";
   DateTime dt = (DateTime)Convert::ChangeType(s, DateTime::typeid);

   Console::WriteLine("The String {0} when converted to a Date is {1}", s, dt);        
}
// The example displays the following output:
//    The Double -2.345 when converted to an Int32 is -2
//    The String 12/12/2009 when converted to a Date is 12/12/2009 12:00:00 AM
using System;

public class ChangeTypeTest {
    public static void Main() {

        Double d = -2.345;
        int i = (int)Convert.ChangeType(d, TypeCode.Int32);

        Console.WriteLine("The Double {0} when converted to an Int32 is {1}", d, i);

        string s = "12/12/2009";
        DateTime dt = (DateTime)Convert.ChangeType(s, typeof(DateTime));

        Console.WriteLine("The String {0} when converted to a Date is {1}", s, dt);        
    }
}
// The example displays the following output:
//    The Double -2.345 when converted to an Int32 is -2
//    The String 12/12/2009 when converted to a Date is 12/12/2009 12:00:00 AM
Public Class ChangeTypeTest
    
    Public Shared Sub Main()
        Dim d As [Double] = - 2.345
        Dim i As Integer = CInt(Convert.ChangeType(d, TypeCode.Int32))
        
        Console.WriteLine("The Double {0} when converted to an Int32 is {1}", d, i)
        Dim s As String = "12/12/2009"
        Dim dt As DateTime = CDate(Convert.ChangeType(s, TypeCode.DateTime))
        
        Console.WriteLine("The String {0} when converted to a Date is {1}", s, dt)
    End Sub 
End Class 
' The example displays the following output:
'    The Double -2.345 when converted to an Int32 is -2
'    The String 12/12/2009 when converted to a Date is 12/12/2009 12:00:00 AM

Poznámky

ChangeType(Object, TypeCode)je metoda převodu pro obecné účely, která převádí objekt určený value na předdefinovaný typ určený parametrem. typeCodeChangeType(Object, TypeCode) is a general-purpose conversion method that converts the object specified by value to a predefined type specified by typeCode. value Parametr může být objekt libovolného typu.The value parameter can be an object of any type. Aby převod mohl být úspěšný, value musí IConvertible implementovat rozhraní, protože metoda jednoduše zabalí volání odpovídající IConvertible metody.For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. Metoda také vyžaduje, aby převod value na typeCode byl podporován.The method also requires that conversion of value to typeCode be supported.

ChangeType(Object, TypeCode) Metoda nepodporujevalue převod na vlastní typ.The ChangeType(Object, TypeCode) method does not support the conversion of value to a custom type. Chcete-li provést převod, zavolejte ChangeType(Object, Type) metodu.To perform such a conversion, call the ChangeType(Object, Type) method.

ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider) ChangeType(Object, Type, IFormatProvider)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object. Parametr poskytuje informace o formátování specifické pro jazykovou verzi.A parameter supplies culture-specific formatting information.

public:
 static System::Object ^ ChangeType(System::Object ^ value, Type ^ conversionType, IFormatProvider ^ provider);
public static object ChangeType (object value, Type conversionType, IFormatProvider provider);
static member ChangeType : obj * Type * IFormatProvider -> obj
Public Shared Function ChangeType (value As Object, conversionType As Type, provider As IFormatProvider) As Object

Parametry

value
Object Object Object Object

Objekt, který implementuje IConvertible rozhraní.An object that implements the IConvertible interface.

conversionType
Type Type Type Type

Typ objektu, který chcete vrátit.The type of object to return.

provider
IFormatProvider IFormatProvider IFormatProvider IFormatProvider

Objekt, který poskytuje informace o formátování specifické pro jazykovou verzi.An object that supplies culture-specific formatting information.

Návraty

Objekt, jehož typ je conversionType a jehož hodnota je valueekvivalentní.An object whose type is conversionType and whose value is equivalent to value.

-nebo--or- value, pokud je Type value aconversionType , je rovno.value, if the Type of value and conversionType are equal.

-nebo--or- Odkaz s hodnotou nullNothing (v Visual Basic), value Pokud null je conversionType a není hodnotovým typem.A null reference (Nothing in Visual Basic), if value is null and conversionType is not a value type.

Výjimky

Tento převod není podporován.This conversion is not supported.

-nebo--or- valueje null aconversionType je typ hodnoty.value is null and conversionType is a value type.

-nebo--or- valueneimplementuje IConvertible rozhraní.value does not implement the IConvertible interface.

valuenení ve formátu pro conversionType providerrozpoznání.value is not in a format for conversionType recognized by provider.

valuepředstavuje číslo, které je mimo rozsah conversionType.value represents a number that is out of the range of conversionType.

Příklady

Následující příklad definuje Temperature třídu, která IConvertible implementuje rozhraní.The following example defines a Temperature class that implements the IConvertible interface.

using namespace System;
using namespace System::Globalization;

public ref class Temperature : IConvertible
{
private:
   Decimal m_Temp;

public:
   Temperature(Decimal temperature)
   {
      m_Temp = temperature;
   }
   
   property Decimal Celsius {
      Decimal get() { return m_Temp; }
   }
   
   property Decimal Kelvin {
      Decimal get() { return m_Temp + (Decimal) 273.15; }
   }
   
   property Decimal Fahrenheit {
      Decimal get() { return Math::Round((Decimal) (m_Temp * 9 / 5 + 32), 2); }
   }
   
   virtual String^ ToString()
   override {
      return m_Temp.ToString("N2") + "�C";
   }

   // IConvertible implementations.
   virtual TypeCode GetTypeCode()
   {
      return TypeCode::Object;
   }
   
   virtual bool ToBoolean(IFormatProvider^ provider) 
   {
      if (m_Temp == 0)
         return false;
      else
         return true;
   } 
   
   virtual Byte ToByte(IFormatProvider^ provider)
   {
      if (m_Temp < Byte::MinValue || m_Temp > Byte::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the Byte type.", 
                                                   m_Temp));
      else
         return Decimal::ToByte(m_Temp);
   }
   
   virtual Char ToChar(IFormatProvider^ provider)
   {
      throw gcnew InvalidCastException("Temperature to Char conversion is not supported.");
   } 
   
   virtual DateTime ToDateTime(IFormatProvider^ provider)
   {
      throw gcnew InvalidCastException("Temperature to DateTime conversion is not supported.");
   }
   
   virtual Decimal ToDecimal(IFormatProvider^ provider)
   {
      return m_Temp;
   }
   
   virtual Double ToDouble(IFormatProvider^ provider)
   {
      return Decimal::ToDouble(m_Temp);
   }   
   
   virtual Int16 ToInt16(IFormatProvider^ provider)
   {
      if (m_Temp < Int16::MinValue || m_Temp > Int16::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the Int16 type.",
                                                   m_Temp));
      else
         return Decimal::ToInt16(m_Temp);
   }
   
   virtual Int32 ToInt32(IFormatProvider^ provider)
      {
      if (m_Temp < Int32::MinValue || m_Temp > Int32::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the Int32 type.",
                                                   m_Temp));
      else
         return Decimal::ToInt32(m_Temp);
   }
   
   virtual Int64 ToInt64(IFormatProvider^ provider)
   {
      if (m_Temp < Int64::MinValue || m_Temp > Int64::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the Int64 type.",
                                                   m_Temp));
      else
         return Decimal::ToInt64(m_Temp);
   }
   
   virtual SByte ToSByte(IFormatProvider^ provider)
   {
      if (m_Temp < SByte::MinValue || m_Temp > SByte::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the SByte type.",
                                                   m_Temp));
      else
         return Decimal::ToSByte(m_Temp);
   }

   virtual Single ToSingle(IFormatProvider^ provider)
   {
      return Decimal::ToSingle(m_Temp);
   }

   virtual String^ ToString(IFormatProvider^ provider)
   {
      return m_Temp.ToString("N2", provider) + "�C";
   }
   
   virtual Object^ ToType(Type^ conversionType, IFormatProvider^ provider)
   {
      switch (Type::GetTypeCode(conversionType))
      {
      case TypeCode::Boolean: 
            return ToBoolean(nullptr);
      case TypeCode::Byte:
            return ToByte(nullptr);
      case TypeCode::Char:
            return ToChar(nullptr);
      case TypeCode::DateTime:
            return ToDateTime(nullptr);
      case TypeCode::Decimal:
            return ToDecimal(nullptr);
      case TypeCode::Double:
            return ToDouble(nullptr);
      case TypeCode::Int16:
            return ToInt16(nullptr);
      case TypeCode::Int32:
            return ToInt32(nullptr);
      case TypeCode::Int64:
            return ToInt64(nullptr);
      case TypeCode::Object:
            if (Temperature::typeid->Equals(conversionType))
               return this;
            else
               throw gcnew InvalidCastException(String::Format("Conversion to a {0} is not supported.",
                                                            conversionType->Name));
      case TypeCode::SByte:
            return ToSByte(nullptr);
      case TypeCode::Single:
            return ToSingle(nullptr);
      case TypeCode::String:
            return ToString(provider);
      case TypeCode::UInt16:
            return ToUInt16(nullptr);
      case TypeCode::UInt32:
            return ToUInt32(nullptr);
      case TypeCode::UInt64:
            return ToUInt64(nullptr);   
         default:
            throw gcnew InvalidCastException(String::Format("Conversion to {0} is not supported.", conversionType->Name));   
      }
   }
   
   virtual UInt16 ToUInt16(IFormatProvider^ provider)
   {
      if (m_Temp < UInt16::MinValue || m_Temp > UInt16::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the UInt16 type.",
                                                   m_Temp));
      else
         return Decimal::ToUInt16(m_Temp);
   }

   virtual UInt32 ToUInt32(IFormatProvider^ provider)
   {
      if (m_Temp < UInt32::MinValue || m_Temp > UInt32::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the UInt32 type.",
                                                   m_Temp));
      else
         return Decimal::ToUInt32(m_Temp);
   }
   
   virtual UInt64 ToUInt64(IFormatProvider^ provider)
   {
      if (m_Temp < UInt64::MinValue || m_Temp > UInt64::MaxValue)
         throw gcnew OverflowException(String::Format("{0} is out of range of the UInt64 type.",
                                                   m_Temp));
      else
         return Decimal::ToUInt64(m_Temp);
   }
};
using System;
using System.Globalization;

public class Temperature : IConvertible
{
   private decimal m_Temp;

   public Temperature(decimal temperature)
   {
      this.m_Temp = temperature;
   }
   
   public decimal Celsius
   {
      get { return this.m_Temp; }   
   }
   
   public decimal Kelvin
   {
      get { return this.m_Temp + 273.15m; }    
   }
   
   public decimal Fahrenheit
   {
      get { return Math.Round((decimal) (this.m_Temp * 9 / 5 + 32), 2); }
   }
   
   public override string ToString()
   {
      return m_Temp.ToString("N2") + "°C";
   }

   // IConvertible implementations.
   public TypeCode GetTypeCode()
   {
      return TypeCode.Object;
   }
   
   public bool ToBoolean(IFormatProvider provider) 
   {
      if (m_Temp == 0)
         return false;
      else
         return true;
   } 
   
   public byte ToByte(IFormatProvider provider)
   {
      if (m_Temp < Byte.MinValue || m_Temp > Byte.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the Byte type.", 
                                                   this.m_Temp));
      else
         return Decimal.ToByte(this.m_Temp);
   }
   
   public char ToChar(IFormatProvider provider)
   {
      throw new InvalidCastException("Temperature to Char conversion is not supported.");
   } 
   
   public DateTime ToDateTime(IFormatProvider provider)
   {
      throw new InvalidCastException("Temperature to DateTime conversion is not supported.");
   }
   
   public decimal ToDecimal(IFormatProvider provider)
   {
      return this.m_Temp;
   }
   
   public double ToDouble(IFormatProvider provider)
   {
      return Decimal.ToDouble(this.m_Temp);
   }   
   
   public short ToInt16(IFormatProvider provider)
   {
      if (this.m_Temp < Int16.MinValue || this.m_Temp > Int16.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the Int16 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToInt16(this.m_Temp);
   }
   
   public int ToInt32(IFormatProvider provider)
      {
      if (this.m_Temp < Int32.MinValue || this.m_Temp > Int32.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the Int32 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToInt32(this.m_Temp);
   }
   
   public long ToInt64(IFormatProvider provider)
   {
      if (this.m_Temp < Int64.MinValue || this.m_Temp > Int64.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the Int64 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToInt64(this.m_Temp);
   }
   
   public sbyte ToSByte(IFormatProvider provider)
   {
      if (this.m_Temp < SByte.MinValue || this.m_Temp > SByte.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the SByte type.",
                                                   this.m_Temp));
      else
         return Decimal.ToSByte(this.m_Temp);
   }

   public float ToSingle(IFormatProvider provider)
   {
      return Decimal.ToSingle(this.m_Temp);
   }

   public string ToString(IFormatProvider provider)
   {
      return m_Temp.ToString("N2", provider) + "°C";
   }
   
   public object ToType(Type conversionType, IFormatProvider provider)
   {
      switch (Type.GetTypeCode(conversionType))
      {
         case TypeCode.Boolean: 
            return this.ToBoolean(null);
         case TypeCode.Byte:
            return this.ToByte(null);
         case TypeCode.Char:
            return this.ToChar(null);
         case TypeCode.DateTime:
            return this.ToDateTime(null);
         case TypeCode.Decimal:
            return this.ToDecimal(null);
         case TypeCode.Double:
            return this.ToDouble(null);
         case TypeCode.Int16:
            return this.ToInt16(null);
         case TypeCode.Int32:
            return this.ToInt32(null);
         case TypeCode.Int64:
            return this.ToInt64(null);
         case TypeCode.Object:
            if (typeof(Temperature).Equals(conversionType))
               return this;
            else
               throw new InvalidCastException(String.Format("Conversion to a {0} is not supported.",
                                                            conversionType.Name));
         case TypeCode.SByte:
            return this.ToSByte(null);
         case TypeCode.Single:
            return this.ToSingle(null);
         case TypeCode.String:
            return this.ToString(provider);
         case TypeCode.UInt16:
            return this.ToUInt16(null);
         case TypeCode.UInt32:
            return this.ToUInt32(null);
         case TypeCode.UInt64:
            return this.ToUInt64(null);   
         default:
            throw new InvalidCastException(String.Format("Conversion to {0} is not supported.", conversionType.Name));   
      }
   }
   
   public ushort ToUInt16(IFormatProvider provider)
   {
      if (this.m_Temp < UInt16.MinValue || this.m_Temp > UInt16.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the UInt16 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToUInt16(this.m_Temp);
   }

   public uint ToUInt32(IFormatProvider provider)
   {
      if (this.m_Temp < UInt32.MinValue || this.m_Temp > UInt32.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the UInt32 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToUInt32(this.m_Temp);
   }
   
   public ulong ToUInt64(IFormatProvider provider)
   {
      if (this.m_Temp < UInt64.MinValue || this.m_Temp > UInt64.MaxValue)
         throw new OverflowException(String.Format("{0} is out of range of the UInt64 type.",
                                                   this.m_Temp));
      else
         return Decimal.ToUInt64(this.m_Temp);
   }
}
Imports System.Globalization

Public Class Temperature : Implements IConvertible
   Private m_Temp As Decimal

   Public Sub New(temperature As Decimal)
      Me.m_Temp = temperature
   End Sub
   
   Public ReadOnly Property Celsius() As Decimal
      Get
         Return Me.m_Temp
      End Get   
   End Property
   
   Public ReadOnly Property Kelvin() As Decimal
      Get
         Return Me.m_Temp + 273.15d   
      End Get
   End Property
   
   Public ReadOnly Property Fahrenheit() As Decimal
      Get
         Return Math.Round(CDec(Me.m_Temp * 9 / 5 + 32), 2)
      End Get      
   End Property
   
   Public Overrides Function ToString() As String
      Return m_Temp.ToString("N2") & "°C"
   End Function

   ' IConvertible implementations.
   Public Function GetTypeCode() As TypeCode _
                   Implements IConvertible.GetTypeCode
      Return TypeCode.Object
   End Function
   
   Public Function ToBoolean(provider As IFormatProvider) As Boolean _
                   Implements IConvertible.ToBoolean
      If m_Temp = 0 Then
         Return False
      Else
         Return True
      End If
   End Function 
   
   Public Function ToByte(provider As IFormatProvider) As Byte _
                   Implements IConvertible.ToByte
      If m_Temp < Byte.MinValue Or m_Temp > Byte.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Byte type.", _ 
                                                   Me.m_Temp)) 
      Else
         Return Decimal.ToByte(Me.m_Temp)
      End If       
   End Function
   
   Public Function ToChar(provider As IFormatProvider) As Char _
                   Implements IConvertible.ToChar
      Throw New InvalidCastException("Temperature to Char conversion is not supported.")
   End Function 
   
   Public Function ToDateTime(provider As IFormatProvider) As Date _
                   Implements IConvertible.ToDateTime
      Throw New InvalidCastException("Temperature to DateTime conversion is not supported.")
   End Function
   
   Public Function ToDecimal(provider As IFormatProvider) As Decimal _
                   Implements IConvertible.ToDecimal
      Return Me.m_Temp
   End Function
   
   Public Function ToDouble(provider As IFormatProvider) As Double _
                   Implements IConvertible.ToDouble
      Return Decimal.ToDouble(Me.m_Temp)
   End Function   
   
   Public Function ToInt16(provider As IFormatProvider) As Int16 _
                   Implements IConvertible.ToInt16
      If Me.m_Temp < Int16.MinValue Or Me.m_Temp > Int16.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int16 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt16(Me.m_Temp)   
      End If
   End Function
   
   Public Function ToInt32(provider As IFormatProvider) As Int32 _
                   Implements IConvertible.ToInt32
      If Me.m_Temp < Int32.MinValue Or Me.m_Temp > Int32.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int32 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt32(Me.m_Temp)
      End If      
   End Function
   
   Public Function ToInt64(provider As IFormatProvider) As Int64 _
                   Implements IConvertible.ToInt64
      If Me.m_Temp < Int64.MinValue Or Me.m_Temp > Int64.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int64 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt64(Me.m_Temp)
      End If      
   End Function
   
   Public Function ToSByte(provider As IFormatProvider) As SByte _
                   Implements IConvertible.ToSByte
      If Me.m_Temp < SByte.MinValue Or Me.m_Temp > SByte.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the SByte type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToSByte(Me.m_Temp)
      End If      
   End Function

   Public Function ToSingle(provider As IFormatProvider) As Single _
                   Implements IConvertible.ToSingle
      Return Decimal.ToSingle(Me.m_Temp)
   End Function

   Public Overloads Function ToString(provider As IFormatProvider) As String _
                   Implements IConvertible.ToString
      Return m_Temp.ToString("N2", provider) & "°C"
   End Function
   
   Public Function ToType(conversionType As Type, provider As IFormatProvider) As Object _
                   Implements IConvertible.ToType
      Select Case Type.GetTypeCode(conversionType)
         Case TypeCode.Boolean 
            Return Me.ToBoolean(Nothing)
         Case TypeCode.Byte
            Return Me.ToByte(Nothing)
         Case TypeCode.Char
            Return Me.ToChar(Nothing)
         Case TypeCode.DateTime
            Return Me.ToDateTime(Nothing)
         Case TypeCode.Decimal
            Return Me.ToDecimal(Nothing)
         Case TypeCode.Double
            Return Me.ToDouble(Nothing)
         Case TypeCode.Int16
            Return Me.ToInt16(Nothing)
         Case TypeCode.Int32
            Return Me.ToInt32(Nothing)
         Case TypeCode.Int64
            Return Me.ToInt64(Nothing)
         Case TypeCode.Object
            If GetType(Temperature).Equals(conversionType) Then
               Return Me
            Else
               Throw New InvalidCastException(String.Format("Conversion to a {0} is not supported.", _
                                                            conversionType.Name))
            End If 
         Case TypeCode.SByte
            Return Me.ToSByte(Nothing)
         Case TypeCode.Single
            Return Me.ToSingle(Nothing)
         Case TypeCode.String
            Return Me.ToString(provider)
         Case TypeCode.UInt16
            Return Me.ToUInt16(Nothing)
         Case TypeCode.UInt32
            Return Me.ToUInt32(Nothing)
         Case TypeCode.UInt64
            Return Me.ToUInt64(Nothing)   
         Case Else
            Throw New InvalidCastException(String.Format("Conversion to {0} is not supported.", conversionType.Name))   
      End Select
   End Function
   
   Public Function ToUInt16(provider As IFormatProvider) As UInt16 _
                   Implements IConvertible.ToUInt16
      If Me.m_Temp < UInt16.MinValue Or Me.m_Temp > UInt16.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt16 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt16(Me.m_Temp)
      End If   
   End Function

   Public Function ToUInt32(provider As IFormatProvider) As UInt32 _
                   Implements IConvertible.ToUInt32
      If Me.m_Temp < UInt32.MinValue Or Me.m_Temp > UInt32.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt32 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt32(Me.m_Temp)
      End If   
   End Function
   
   Public Function ToUInt64(provider As IFormatProvider) As UInt64 _
                   Implements IConvertible.ToUInt64
      If Me.m_Temp < UInt64.MinValue Or Me.m_Temp > UInt64.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt64 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt64(Me.m_temp)
      End If   
   End Function
End Class

Následující příklad vytvoří instanci Temperature třídy a ChangeType(Object, Type, IFormatProvider) zavolá metodu pro její převedení na základní číselné typy podporované .NET Framework a na String.The following example creates an instance of the Temperature class and calls the ChangeType(Object, Type, IFormatProvider) method to convert it to the basic numeric types supported by the .NET Framework and to a String. Ukazuje, že ChangeType metoda zabalí volání do IConvertible implementace zdrojového typu.It illustrates that the ChangeType method wraps a call to the source type's IConvertible implementation.

void main()
{     
   Temperature^ cool = gcnew Temperature(5);
   array<Type^>^ targetTypes = gcnew array<Type^> { SByte::typeid, Int16::typeid, Int32::typeid,
                                                    Int64::typeid, Byte::typeid, UInt16::typeid,
                                                    UInt32::typeid, UInt64::typeid, Decimal::typeid,
                                                    Single::typeid, Double::typeid, String::typeid };
   CultureInfo^ provider = gcnew CultureInfo("fr-FR");
      
   for each (Type^ targetType in targetTypes)
   {
      try {
         Object^ value = Convert::ChangeType(cool, targetType, provider);
         Console::WriteLine("Converted {0} {1} to {2} {3}.",
                           cool->GetType()->Name, cool->ToString(),
                           targetType->Name, value);
      }
      catch (InvalidCastException^) {
         Console::WriteLine("Unsupported {0} --> {1} conversion.",
                           cool->GetType()->Name, targetType->Name);
      }                     
      catch (OverflowException^) {
         Console::WriteLine("{0} is out of range of the {1} type.",
                           cool, targetType->Name);
      }
   }
}
// The example dosplays the following output:
//       Converted Temperature 5.00�C to SByte 5.
//       Converted Temperature 5.00�C to Int16 5.
//       Converted Temperature 5.00�C to Int32 5.
//       Converted Temperature 5.00�C to Int64 5.
//       Converted Temperature 5.00�C to Byte 5.
//       Converted Temperature 5.00�C to UInt16 5.
//       Converted Temperature 5.00�C to UInt32 5.
//       Converted Temperature 5.00�C to UInt64 5.
//       Converted Temperature 5.00�C to Decimal 5.
//       Converted Temperature 5.00�C to Single 5.
//       Converted Temperature 5.00�C to Double 5.
//       Converted Temperature 5.00�C to String 5,00�C.
public class Example
{
   public static void Main()
   {
      Temperature cool = new Temperature(5);
      Type[] targetTypes = { typeof(SByte), typeof(Int16), typeof(Int32),
                             typeof(Int64), typeof(Byte), typeof(UInt16),
                             typeof(UInt32), typeof(UInt64), typeof(Decimal),
                             typeof(Single), typeof(Double), typeof(String) };
      CultureInfo provider = new CultureInfo("fr-FR");
      
      foreach (Type targetType in targetTypes)
      {
         try {
            object value = Convert.ChangeType(cool, targetType, provider);
            Console.WriteLine("Converted {0} {1} to {2} {3}.",
                              cool.GetType().Name, cool.ToString(),
                              targetType.Name, value);
         }
         catch (InvalidCastException) {
            Console.WriteLine("Unsupported {0} --> {1} conversion.",
                              cool.GetType().Name, targetType.Name);
         }                     
         catch (OverflowException) {
            Console.WriteLine("{0} is out of range of the {1} type.",
                              cool, targetType.Name);
         }
      }
   }
}
// The example dosplays the following output:
//       Converted Temperature 5.00°C to SByte 5.
//       Converted Temperature 5.00°C to Int16 5.
//       Converted Temperature 5.00°C to Int32 5.
//       Converted Temperature 5.00°C to Int64 5.
//       Converted Temperature 5.00°C to Byte 5.
//       Converted Temperature 5.00°C to UInt16 5.
//       Converted Temperature 5.00°C to UInt32 5.
//       Converted Temperature 5.00°C to UInt64 5.
//       Converted Temperature 5.00°C to Decimal 5.
//       Converted Temperature 5.00°C to Single 5.
//       Converted Temperature 5.00°C to Double 5.
//       Converted Temperature 5.00°C to String 5,00°C.
Module Example
   Public Sub Main()
      Dim cool As New Temperature(5)
      Dim targetTypes() As Type = { GetType(SByte), GetType(Int16), GetType(Int32), _
                                    GetType(Int64), GetType(Byte), GetType(UInt16), _
                                    GetType(UInt32), GetType(UInt64), GetType(Decimal), _
                                    GetType(Single), GetType(Double), GetType(String) }
      Dim provider As New CultureInfo("fr-FR")
      
      For Each targetType As Type In targetTypes
         Try
            Dim value As Object = Convert.ChangeType(cool, targetType, provider)
            Console.WriteLine("Converted {0} {1} to {2} {3}.", _
                              cool.GetType().Name, cool.ToString(), _
                              targetType.Name, value)
         Catch e As InvalidCastException
            Console.WriteLine("Unsupported {0} --> {1} conversion.", _
                              cool.GetType().Name, targetType.Name)
         Catch e As OverflowException
            Console.WriteLine("{0} is out of range of the {1} type.", _
                              cool, targetType.Name)
         End Try                     
      Next
   End Sub
End Module
' The example displays the following output:
'       Converted Temperature 5.00°C to SByte 5.
'       Converted Temperature 5.00°C to Int16 5.
'       Converted Temperature 5.00°C to Int32 5.
'       Converted Temperature 5.00°C to Int64 5.
'       Converted Temperature 5.00°C to Byte 5.
'       Converted Temperature 5.00°C to UInt16 5.
'       Converted Temperature 5.00°C to UInt32 5.
'       Converted Temperature 5.00°C to UInt64 5.
'       Converted Temperature 5.00°C to Decimal 5.
'       Converted Temperature 5.00°C to Single 5.
'       Converted Temperature 5.00°C to Double 5.
'       Converted Temperature 5.00°C to String 5,00°C.

Poznámky

ChangeTypeje metoda převodu pro obecné účely, která převádí objekt určený parametrem value na conversionType.ChangeType is a general-purpose conversion method that converts the object specified by value to conversionType. Parametr může být objekt libovolného typu a conversionType může také být Type objekt, který představuje libovolný základní nebo vlastní typ. valueThe value parameter can be an object of any type, and conversionType can also be a Type object that represents any base or custom type. Aby převod mohl být úspěšný, value musí IConvertible implementovat rozhraní, protože metoda jednoduše zabalí volání odpovídající IConvertible metody.For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. Metoda vyžaduje, aby byl převod value na conversionType , který je podporován.The method requires that conversion of value to conversionType be supported.

provider ParametrIFormatProvider je implementace, která poskytuje informace o formátování pro převod.The provider parameter is an IFormatProvider implementation that supplies formatting information for the conversion. Určuje, zda je tento parametr použit a který závisí na IConvertible základní implementaci.Whether and how this parameter is used depends on the underlying IConvertible implementation. Pokud value je základní datový typ, provider používá se pouze pro následující převody:If value is a base data type, provider is used only for the following conversions:

Pokud value je typ definovaný aplikací, jeho IConvertible implementace může použít provider parametr.If value is an application-defined type, its IConvertible implementation may use the provider parameter.

Poznámky pro volající

ChangeType(Object, Type, IFormatProvider) Metoda může převést hodnotu výčtu na jiný typ.The ChangeType(Object, Type, IFormatProvider) method can convert an enumeration value to another type. Nemůže však převést jiný typ na hodnotu výčtu, i když je typ zdroje základní typ výčtu.However, it cannot convert another type to an enumeration value, even if the source type is the underlying type of the enumeration. Chcete-li převést typ na hodnotu výčtu, použijte operátor přetypování (in C#) nebo funkci pro převod (v Visual Basic).To convert a type to an enumeration value, use a casting operator (in C#) or a conversion function (in Visual Basic). Následující příklad ukazuje převod na a z hodnoty výčtu kontinentu .The following example illustrates the conversion to and from a Continent enumeration value.

[!code-csharpSystem.Convert.ChangeType#5] [!code-vbSystem.Convert.ChangeType#5][!code-csharpSystem.Convert.ChangeType#5] [!code-vbSystem.Convert.ChangeType#5] ChangeType(Object, Type, IFormatProvider) Metoda může převést typ s povolenou hodnotou null na jiný typ.The ChangeType(Object, Type, IFormatProvider) method can convert a nullable type to another type. Nemůže však převést jiný typ na hodnotu typu s možnou hodnotou null, i když conversionType je základní typ. Nullable<T>However, it cannot convert another type to a value of a nullable type, even if conversionType is the underlying type of the Nullable<T>. Chcete-li provést převod, můžete použít operátor přetypování (v C#) nebo funkci konverze (v Visual Basic).To perform the conversion, you can use a casting operator (in C#) or a conversion function (in Visual Basic). Následující příklad ukazuje převod na typ a z typu s možnou hodnotou null.The following example illustrates the conversion to and from a nullable type.

[! Code-CSharpSystem. Reconvert. ChangeType # 8] [! Code-VBSystem. Reconvert. ChangeType # 8][!code-csharpSystem.Convert.ChangeType#8] [!code-vbSystem.Convert.ChangeType#8]

ChangeType(Object, TypeCode, IFormatProvider) ChangeType(Object, TypeCode, IFormatProvider) ChangeType(Object, TypeCode, IFormatProvider)

Vrátí objekt zadaného typu, jehož hodnota je ekvivalentní specifikovanému objektu.Returns an object of the specified type whose value is equivalent to the specified object. Parametr poskytuje informace o formátování specifické pro jazykovou verzi.A parameter supplies culture-specific formatting information.

public:
 static System::Object ^ ChangeType(System::Object ^ value, TypeCode typeCode, IFormatProvider ^ provider);
public static object ChangeType (object value, TypeCode typeCode, IFormatProvider provider);
static member ChangeType : obj * TypeCode * IFormatProvider -> obj

Parametry

value
Object Object Object Object

Objekt, který implementuje IConvertible rozhraní.An object that implements the IConvertible interface.

typeCode
TypeCode TypeCode TypeCode TypeCode

Typ objektu, který chcete vrátit.The type of object to return.

provider
IFormatProvider IFormatProvider IFormatProvider IFormatProvider

Objekt, který poskytuje informace o formátování specifické pro jazykovou verzi.An object that supplies culture-specific formatting information.

Návraty

Objekt, jehož nadřízený typ je typeCode a jehož hodnota je valueekvivalentní.An object whose underlying type is typeCode and whose value is equivalent to value.

-nebo--or- Odkaz s hodnotou nullNothing (v Visual Basic), value Pokud null je typeCode a Emptyje String, nebo Object.A null reference (Nothing in Visual Basic), if value is null and typeCode is Empty, String, or Object.

Výjimky

Tento převod není podporován.This conversion is not supported.

-nebo--or- valueje null atypeCode určuje typ hodnoty.value is null and typeCode specifies a value type.

-nebo--or- valueneimplementuje IConvertible rozhraní.value does not implement the IConvertible interface.

valuenení ve formátu pro typeCode typ providerrozpoznávaný.value is not in a format for the typeCode type recognized by provider.

valuepředstavuje číslo, které je mimo rozsah typeCode typu.value represents a number that is out of the range of the typeCode type.

Formát typeCode je neplatný.typeCode is invalid.

Příklady

Následující příklad definuje poskytovatele vlastního InterceptProvider formátu s názvem, který označuje, kdy GetFormat NumberFormatInfo je jeho metoda volána, a vrátí hodnotu DateTimeFormatInfo pro jazykovou verzi fr-FR a objekt pro jazykovou verzi en-US.The following example defines a custom format provider named InterceptProvider that indicates when its GetFormat method is called and returns a NumberFormatInfo for the fr-FR culture and a DateTimeFormatInfo object for the en-US culture. Tento zprostředkovatel formátu se používá ve všech voláních ChangeType(Object, TypeCode, IFormatProvider) metody.This format provider is used in all calls to the ChangeType(Object, TypeCode, IFormatProvider) method. Příklad Double poté vytvoří pole s DateTime hodnotou a a provede opakované volání ChangeType(Object, TypeCode, IFormatProvider) TypeCode s každou hodnotou a každým členem výčtu.The example then creates an array with a Double and a DateTime value and makes repeated calls to ChangeType(Object, TypeCode, IFormatProvider) with each value and each member of the TypeCode enumeration. Příklad ukazuje, že metoda používá IFormatProvider parametr a také ukazuje použití provider parametru k provádění formátování zohledňující jazykovou verzi.The example illustrates when the method uses the IFormatProvider parameter and also illustrates the use of the provider parameter to perform culture-sensitive formatting.

using namespace System;
using namespace System::Globalization;

ref class InterceptProvider : IFormatProvider
{
public: 
   virtual Object^ GetFormat(Type^ formatType) 
   {
      CultureInfo^ culture;
      if (formatType == NumberFormatInfo::typeid) {
         Console::WriteLine("   Returning a fr-FR numeric format provider.");
         
         culture = gcnew CultureInfo("fr-FR");
         return culture->NumberFormat;
      }  
      else if (formatType == DateTimeFormatInfo::typeid) {
         Console::WriteLine("   Returning an en-US date/time format provider.");
         culture = gcnew CultureInfo("en-US");
         return culture->DateTimeFormat;
      }
      else {
         Console::WriteLine("   Requesting a format provider of {0}.", formatType->Name);
         return nullptr;
      }
   }
};

void main()
{
   array<Object^>^ values = gcnew array<Object^> { 103.5, gcnew DateTime(2010, 12, 26, 14, 34, 0) };
   IFormatProvider^ provider = gcnew InterceptProvider();
      
   // Convert value to each of the types represented in TypeCode enum.
   for each (Object^ value in values)
   {
      // Iterate types in TypeCode enum.
      for each (TypeCode enumType in (array<TypeCode>^) Enum::GetValues(TypeCode::typeid))
      {         
         if (enumType == TypeCode::DBNull || enumType == TypeCode::Empty) continue;
            
         try {
            Console::WriteLine("{0} ({1}) --> {2} ({3}).", 
                              value, value->GetType()->Name,
                              Convert::ChangeType(value, enumType, provider),
                              enumType.ToString());
         }
         catch (InvalidCastException^ e) {
            Console::WriteLine("Cannot convert a {0} to a {1}",
                              value->GetType()->Name, enumType.ToString());
         }                     
         catch (OverflowException^ e) {
            Console::WriteLine("Overflow: {0} is out of the range of a {1}",
                              value, enumType.ToString());
         }
      }
      Console::WriteLine();
   }
}
// The example displays the following output:
//    103.5 (Double) --> 103.5 (Object).
//    103.5 (Double) --> True (Boolean).
//    Cannot convert a Double to a Char
//    103.5 (Double) --> 104 (SByte).
//    103.5 (Double) --> 104 (Byte).
//    103.5 (Double) --> 104 (Int16).
//    103.5 (Double) --> 104 (UInt16).
//    103.5 (Double) --> 104 (Int32).
//    103.5 (Double) --> 104 (UInt32).
//    103.5 (Double) --> 104 (Int64).
//    103.5 (Double) --> 104 (UInt64).
//    103.5 (Double) --> 103.5 (Single).
//    103.5 (Double) --> 103.5 (Double).
//    103.5 (Double) --> 103.5 (Decimal).
//    Cannot convert a Double to a DateTime
//       Returning a fr-FR numeric format provider.
//    103.5 (Double) --> 103,5 (String).
//    
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (Object).
//    Cannot convert a DateTime to a Boolean
//    Cannot convert a DateTime to a Char
//    Cannot convert a DateTime to a SByte
//    Cannot convert a DateTime to a Byte
//    Cannot convert a DateTime to a Int16
//    Cannot convert a DateTime to a UInt16
//    Cannot convert a DateTime to a Int32
//    Cannot convert a DateTime to a UInt32
//    Cannot convert a DateTime to a Int64
//    Cannot convert a DateTime to a UInt64
//    Cannot convert a DateTime to a Single
//    Cannot convert a DateTime to a Double
//    Cannot convert a DateTime to a Decimal
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (DateTime).
//       Returning an en-US date/time format provider.
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (String).
using System;
using System.Globalization;

public class InterceptProvider : IFormatProvider
{
   public object GetFormat(Type formatType) 
   {
      if (formatType == typeof(NumberFormatInfo)) {
         Console.WriteLine("   Returning a fr-FR numeric format provider.");
         return new System.Globalization.CultureInfo("fr-FR").NumberFormat;
      }   
      else if (formatType == typeof(DateTimeFormatInfo)) {
         Console.WriteLine("   Returning an en-US date/time format provider.");
         return new System.Globalization.CultureInfo("en-US").DateTimeFormat;
      }
      else {
         Console.WriteLine("   Requesting a format provider of {0}.", formatType.Name);
         return null;
      }
   }
}

public class Example
{
   public static void Main()
   {
      object[] values = { 103.5d, new DateTime(2010, 12, 26, 14, 34, 0) };
      IFormatProvider provider = new InterceptProvider();
      
      // Convert value to each of the types represented in TypeCode enum.
      foreach (object value in values)
      {
         // Iterate types in TypeCode enum.
         foreach (TypeCode enumType in ((TypeCode[]) Enum.GetValues(typeof(TypeCode))))
         {         
            if (enumType == TypeCode.DBNull || enumType == TypeCode.Empty) continue;
            
            try {
               Console.WriteLine("{0} ({1}) --> {2} ({3}).", 
                                 value, value.GetType().Name,
                                 Convert.ChangeType(value, enumType, provider),
                                 enumType.ToString());
            }
            catch (InvalidCastException) {
               Console.WriteLine("Cannot convert a {0} to a {1}",
                                 value.GetType().Name, enumType.ToString());
            }                     
            catch (OverflowException) {
               Console.WriteLine("Overflow: {0} is out of the range of a {1}",
                                 value, enumType.ToString());
            }
         }
         Console.WriteLine();
      }
   }
}
// The example displays the following output:
//    103.5 (Double) --> 103.5 (Object).
//    103.5 (Double) --> True (Boolean).
//    Cannot convert a Double to a Char
//    103.5 (Double) --> 104 (SByte).
//    103.5 (Double) --> 104 (Byte).
//    103.5 (Double) --> 104 (Int16).
//    103.5 (Double) --> 104 (UInt16).
//    103.5 (Double) --> 104 (Int32).
//    103.5 (Double) --> 104 (UInt32).
//    103.5 (Double) --> 104 (Int64).
//    103.5 (Double) --> 104 (UInt64).
//    103.5 (Double) --> 103.5 (Single).
//    103.5 (Double) --> 103.5 (Double).
//    103.5 (Double) --> 103.5 (Decimal).
//    Cannot convert a Double to a DateTime
//       Returning a fr-FR numeric format provider.
//    103.5 (Double) --> 103,5 (String).
//    
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (Object).
//    Cannot convert a DateTime to a Boolean
//    Cannot convert a DateTime to a Char
//    Cannot convert a DateTime to a SByte
//    Cannot convert a DateTime to a Byte
//    Cannot convert a DateTime to a Int16
//    Cannot convert a DateTime to a UInt16
//    Cannot convert a DateTime to a Int32
//    Cannot convert a DateTime to a UInt32
//    Cannot convert a DateTime to a Int64
//    Cannot convert a DateTime to a UInt64
//    Cannot convert a DateTime to a Single
//    Cannot convert a DateTime to a Double
//    Cannot convert a DateTime to a Decimal
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (DateTime).
//       Returning an en-US date/time format provider.
//    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (String).
Imports System.Globalization

Public Class InterceptProvider : Implements IFormatProvider
   Public Function GetFormat(formatType As Type) As Object _
          Implements IFormatProvider.GetFormat
      If formatType.Equals(GetType(NumberFormatInfo)) Then
         Console.WriteLine("   Returning a fr-FR numeric format provider.")
         Return New CultureInfo("fr-FR").NumberFormat
      ElseIf formatType.Equals(GetType(DateTimeFormatInfo)) Then
         Console.WriteLine("   Returning an en-US date/time format provider.")
         Return New CultureInfo("en-US").DateTimeFormat
      Else
         Console.WriteLine("   Requesting a format provider of {0}.", formatType.Name)
         Return Nothing
      End If
   End Function
End Class

Module Example
   Public Sub Main()
      Dim values() As Object = { 103.5r, #12/26/2010 2:34PM# }
      Dim provider As New InterceptProvider()
      
      ' Convert value to each of the types represented in TypeCode enum.
      For Each value As Object In values
         ' Iterate types in TypeCode enum.
         For Each enumType As TypeCode In DirectCast([Enum].GetValues(GetType(TypeCode)), TypeCode())         
            If enumType = TypeCode.DbNull Or enumType = TypeCode.Empty Then Continue For
            
            Try
               Console.WriteLine("{0} ({1}) --> {2} ({3}).", _
                                 value, value.GetType().Name, _
                                 Convert.ChangeType(value, enumType, provider), _
                                 enumType.ToString())
            Catch e As InvalidCastException
               Console.WriteLine("Cannot convert a {0} to a {1}", _
                                 value.GetType().Name, enumType.ToString())
            Catch e As OverflowException
               Console.WriteLine("Overflow: {0} is out of the range of a {1}", _
                                 value, enumType.ToString())
            End Try
         Next
         Console.WriteLine()
      Next
   End Sub
End Module
' The example displays the following output:
'    103.5 (Double) --> 103.5 (Object).
'    103.5 (Double) --> True (Boolean).
'    Cannot convert a Double to a Char
'    103.5 (Double) --> 104 (SByte).
'    103.5 (Double) --> 104 (Byte).
'    103.5 (Double) --> 104 (Int16).
'    103.5 (Double) --> 104 (UInt16).
'    103.5 (Double) --> 104 (Int32).
'    103.5 (Double) --> 104 (UInt32).
'    103.5 (Double) --> 104 (Int64).
'    103.5 (Double) --> 104 (UInt64).
'    103.5 (Double) --> 103.5 (Single).
'    103.5 (Double) --> 103.5 (Double).
'    103.5 (Double) --> 103.5 (Decimal).
'    Cannot convert a Double to a DateTime
'       Returning a fr-FR numeric format provider.
'    103.5 (Double) --> 103,5 (String).
'    
'    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (Object).
'    Cannot convert a DateTime to a Boolean
'    Cannot convert a DateTime to a Char
'    Cannot convert a DateTime to a SByte
'    Cannot convert a DateTime to a Byte
'    Cannot convert a DateTime to a Int16
'    Cannot convert a DateTime to a UInt16
'    Cannot convert a DateTime to a Int32
'    Cannot convert a DateTime to a UInt32
'    Cannot convert a DateTime to a Int64
'    Cannot convert a DateTime to a UInt64
'    Cannot convert a DateTime to a Single
'    Cannot convert a DateTime to a Double
'    Cannot convert a DateTime to a Decimal
'    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (DateTime).
'       Returning an en-US date/time format provider.
'    12/26/2010 2:34:00 PM (DateTime) --> 12/26/2010 2:34:00 PM (String).

Poznámky

ChangeType(Object, TypeCode, IFormatProvider)je metoda převodu pro obecné účely, která převádí objekt určený value na předdefinovaný typ určený parametrem. typeCodeChangeType(Object, TypeCode, IFormatProvider) is a general-purpose conversion method that converts the object specified by value to a predefined type specified by typeCode. value Parametr může být objekt libovolného typu.The value parameter can be an object of any type. Aby převod mohl být úspěšný, value musí IConvertible implementovat rozhraní, protože metoda jednoduše zabalí volání odpovídající IConvertible metody.For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. Metoda také vyžaduje, aby převod value na typeCode byl podporován.The method also requires that conversion of value to typeCode be supported.

ChangeType(Object, TypeCode, IFormatProvider) Metoda nepodporujevalue převod na vlastní typ.The ChangeType(Object, TypeCode, IFormatProvider) method does not support the conversion of value to a custom type. Chcete-li provést převod, zavolejte ChangeType(Object, Type, IFormatProvider) metodu.To perform such a conversion, call the ChangeType(Object, Type, IFormatProvider) method.

provider ParametrIFormatProvider je implementace, která poskytuje informace o formátování pro převod.The provider parameter is an IFormatProvider implementation that supplies formatting information for the conversion. Určuje, zda je tento parametr použit a který závisí na IConvertible základní implementaci.Whether and how this parameter is used depends on the underlying IConvertible implementation. Pokud value je základní datový typ, provider používá se pouze pro následující převody.If value is a base data type, provider is used only for the following conversions. Pokud je předánCultureInfo argument do těchto metod, je použit objekt, který představuje aktuální jazykovou verzi vlákna. IFormatProvider nullIf a nullIFormatProvider argument is passed to these methods, the CultureInfo object that represents the current thread culture is used.

Pokud value je typ definovaný aplikací, jeho IConvertible implementace může použít provider parametr.If value is an application-defined type, its IConvertible implementation may use the provider parameter.

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