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

定義

指定されたオブジェクトと等しい値を持つ、指定された型のオブジェクトを返します。Returns an object of a specified type whose value is equivalent to a specified object.

オーバーロード

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

指定されたオブジェクトと等しい値を持つ、指定された型のオブジェクトを返します。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)

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。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)

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。Returns an object of the specified type whose value is equivalent to the specified object. パラメーターにより、カルチャに固有の書式情報が指定されます。A parameter supplies culture-specific formatting information.

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

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。Returns an object of the specified type whose value is equivalent to the specified object. パラメーターにより、カルチャに固有の書式情報が指定されます。A parameter supplies culture-specific formatting information.

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

指定されたオブジェクトと等しい値を持つ、指定された型のオブジェクトを返します。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

パラメーター

value
Object Object Object Object

IConvertible インターフェイスを実装するオブジェクト。An object that implements the IConvertible interface.

conversionType
Type Type Type Type

返すオブジェクトの型。The type of object to return.

戻り値

型が conversionType であり、value と等価の値を持つオブジェクト。An object whose type is conversionType and whose value is equivalent to value.

または-or- valuenull で、conversionType が値型ではない場合は、null 参照 (Visual Basic の場合は Nothing)。A null reference (Nothing in Visual Basic), if value is null and conversionType is not a value type.

例外

この変換はサポートされていません。This conversion is not supported.

または-or- valuenull で、conversionType が値型です。value is null and conversionType is a value type.

または-or- valueIConvertible インターフェイスを実装していません。value does not implement the IConvertible interface.

valueconversionType によって認識される形式ではありません。value is not in a format recognized by conversionType.

valueconversionType の範囲外にある数値を表します。value represents a number that is out of the range of conversionType.

conversionTypenullです。conversionType is null.

ChangeType メソッドの使用例を次に示します。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);        
    }
}
Imports System

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 'Main
End Class 'ChangeTypeTest

注釈

ChangeType 指定されたオブジェクトを変換する汎用変換メソッドは、valueconversionTypeします。ChangeType is a general-purpose conversion method that converts the object specified by value to conversionType. valueパラメーターは、任意の型のオブジェクトであることができますとconversionTypeすることもできます、Type任意の基本またはカスタム型を表すオブジェクト。The value parameter can be an object of any type, and conversionType can also be a Type object that represents any base or custom type. 変換には、成功のvalue実装する必要があります、IConvertibleインターフェイス、メソッドは単に、適切な呼び出しをラップしますのでIConvertibleメソッド。For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. メソッドの変換を必要とvalueconversionTypeサポートされます。The method requires that conversion of value to conversionType be supported.

このメソッドは、変換を現在のスレッドのカルチャを使用します。This method uses the current thread's culture for the conversion.

注意 (呼び出し元)

ChangeType(Object, Type)メソッドが列挙値を別の型に変換できます。The ChangeType(Object, Type) method can convert an enumeration value to another type. ただし、場合でも、元の型が列挙体の基になる型を列挙値では、別の型を変換ができません。However, it cannot convert another type to an enumeration value, even if the source type is the underlying type of the enumeration. 型を列挙値に変換するには、キャスト演算子 (C# の場合) または (Visual Basic) での変換関数を使用します。To convert a type to an enumeration value, use a casting operator (in C#) or a conversion function (in Visual Basic). 次の例との間に変換を示しています、大陸列挙値。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)メソッドが null 許容型を別の型に変換できます。The ChangeType(Object, Type) method can convert a nullable type to another type. ただし、別の型、null 許容型の値に変換できない場合でもconversionTypeの基になる型には、Nullable<T>します。変換を実行するには、キャスト演算子 (C# で) または (Visual Basic) での変換関数を使用できます。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). 次の例は、null 許容型との間の変換を示しています。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)

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。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

パラメーター

value
Object Object Object Object

IConvertible インターフェイスを実装するオブジェクト。An object that implements the IConvertible interface.

typeCode
TypeCode TypeCode TypeCode TypeCode

返すオブジェクトの型。The type of object to return.

戻り値

基になる型が typeCode であり、value と等価の値を持つオブジェクト。An object whose underlying type is typeCode and whose value is equivalent to value.

または-or- valuenull で、typeCodeEmptyString、または Object の場合は、null 参照 (Visual Basic の場合は Nothing)。A null reference (Nothing in Visual Basic), if value is null and typeCode is Empty, String, or Object.

例外

この変換はサポートされていません。This conversion is not supported.

または-or- valuenull であり、typeCode は値の型を指定します。value is null and typeCode specifies a value type.

または-or- valueIConvertible インターフェイスを実装していません。value does not implement the IConvertible interface.

valuetypeCode 型によって認識される形式ではありません。value is not in a format recognized by the typeCode type.

valuetypeCode 型の範囲外にある数値を表します。value represents a number that is out of the range of the typeCode type.

typeCode が無効です。typeCode is invalid.

次の例を使用する方法を示しています、ChangeType(Object, TypeCode)を変更するメソッド、Objectで指定された型をTypeCode可能であれば、パラメーター。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
Imports System

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

注釈

ChangeType(Object, TypeCode) 指定されたオブジェクトを変換する汎用変換メソッドは、valueで指定された定義済みの型をtypeCodeします。ChangeType(Object, TypeCode) is a general-purpose conversion method that converts the object specified by value to a predefined type specified by typeCode. valueパラメーターは任意の型のオブジェクトであることができます。The value parameter can be an object of any type. 変換には、成功のvalue実装する必要があります、IConvertibleインターフェイス、メソッドは単に、適切な呼び出しをラップしますのでIConvertibleメソッド。For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. メソッドは、そのへの変換も必要があります。valuetypeCodeサポートされます。The method also requires that conversion of value to typeCode be supported.

ChangeType(Object, TypeCode)メソッドへの変換をサポートしていませんvalueをカスタム型。The ChangeType(Object, TypeCode) method does not support the conversion of value to a custom type. このような変換を実行するのには、呼び出し、ChangeType(Object, Type)メソッド。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)

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。Returns an object of the specified type whose value is equivalent to the specified object. パラメーターにより、カルチャに固有の書式情報が指定されます。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

パラメーター

value
Object Object Object Object

IConvertible インターフェイスを実装するオブジェクト。An object that implements the IConvertible interface.

conversionType
Type Type Type Type

返すオブジェクトの型。The type of object to return.

provider
IFormatProvider IFormatProvider IFormatProvider IFormatProvider

カルチャ固有の書式情報を提供するオブジェクト。An object that supplies culture-specific formatting information.

戻り値

型が conversionType であり、value と等価の値を持つオブジェクト。An object whose type is conversionType and whose value is equivalent to value.

または-or- valueTypeconversionType が等しい場合は valuevalue, if the Type of value and conversionType are equal.

または-or- valuenull で、conversionType が値型ではない場合は、null 参照 (Visual Basic の場合は Nothing)。A null reference (Nothing in Visual Basic), if value is null and conversionType is not a value type.

例外

この変換はサポートされていません。This conversion is not supported.

または-or- valuenull で、conversionType が値型です。value is null and conversionType is a value type.

または-or- valueIConvertible インターフェイスを実装していません。value does not implement the IConvertible interface.

value は、provider によって認識される conversionType の形式ではありません。value is not in a format for conversionType recognized by provider.

valueconversionType の範囲外にある数値を表します。value represents a number that is out of the range of conversionType.

conversionTypenullです。conversionType is null.

次の例では、 Temperature インターフェイスを実装する IConvertible クラスを定義しています。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

次の例のインスタンスを作成する、Temperatureクラスと呼び出し、ChangeType(Object, Type, IFormatProvider)サポートされている .NET Framework とに基本的な数値型に変換するメソッド、Stringします。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. 示しています、ChangeTypeメソッドは、ソースの種類への呼び出しをラップしますIConvertible実装します。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.

注釈

ChangeType 指定されたオブジェクトを変換する汎用変換メソッドは、valueconversionTypeします。ChangeType is a general-purpose conversion method that converts the object specified by value to conversionType. valueパラメーターは、任意の型のオブジェクトであることができますとconversionTypeすることもできます、Type任意の基本またはカスタム型を表すオブジェクト。The value parameter can be an object of any type, and conversionType can also be a Type object that represents any base or custom type. 変換には、成功のvalue実装する必要があります、IConvertibleインターフェイス、メソッドは単に、適切な呼び出しをラップしますのでIConvertibleメソッド。For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. メソッドの変換を必要とvalueconversionTypeサポートされます。The method requires that conversion of value to conversionType be supported.

providerパラメーターは、IFormatProvider変換のための書式設定情報を提供します。The provider parameter is an IFormatProvider implementation that supplies formatting information for the conversion. このパラメーターが使用されるかどうか、どのように、基になる依存IConvertible実装します。Whether and how this parameter is used depends on the underlying IConvertible implementation. 場合value基本データ型は、provider次の変換にのみ使用されます。If value is a base data type, provider is used only for the following conversions:

場合valueがアプリケーション定義の型の場合は、そのIConvertible実装を使用して、可能性があります、providerパラメーター。If value is an application-defined type, its IConvertible implementation may use the provider parameter.

注意 (呼び出し元)

ChangeType(Object, Type, IFormatProvider)メソッドが列挙値を別の型に変換できます。The ChangeType(Object, Type, IFormatProvider) method can convert an enumeration value to another type. ただし、場合でも、元の型が列挙体の基になる型を列挙値では、別の型を変換ができません。However, it cannot convert another type to an enumeration value, even if the source type is the underlying type of the enumeration. 型を列挙値に変換するには、キャスト演算子 (C# の場合) または (Visual Basic) での変換関数を使用します。To convert a type to an enumeration value, use a casting operator (in C#) or a conversion function (in Visual Basic). 次の例との間に変換を示しています、大陸列挙値。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)メソッドが null 許容型を別の型に変換できます。The ChangeType(Object, Type, IFormatProvider) method can convert a nullable type to another type. ただし、別の型、null 許容型の値に変換できない場合でもconversionTypeの基になる型には、Nullable<T>します。However, it cannot convert another type to a value of a nullable type, even if conversionType is the underlying type of the Nullable<T>. 変換を実行するには、キャスト演算子 (C# で) または (Visual Basic) での変換関数を使用できます。To perform the conversion, you can use a casting operator (in C#) or a conversion function (in Visual Basic). 次の例は、null 許容型との間の変換を示しています。The following example illustrates the conversion to and from a nullable type.

[!code-csharpSystem.Convert.ChangeType#8] [!code-vbSystem.Convert.ChangeType#8][!code-csharpSystem.Convert.ChangeType#8] [!code-vbSystem.Convert.ChangeType#8]

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

指定したオブジェクトに等しい値を持つ指定した型のオブジェクトを返します。Returns an object of the specified type whose value is equivalent to the specified object. パラメーターにより、カルチャに固有の書式情報が指定されます。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

パラメーター

value
Object Object Object Object

IConvertible インターフェイスを実装するオブジェクト。An object that implements the IConvertible interface.

typeCode
TypeCode TypeCode TypeCode TypeCode

返すオブジェクトの型。The type of object to return.

provider
IFormatProvider IFormatProvider IFormatProvider IFormatProvider

カルチャ固有の書式情報を提供するオブジェクト。An object that supplies culture-specific formatting information.

戻り値

基になる型が typeCode であり、value と等価の値を持つオブジェクト。An object whose underlying type is typeCode and whose value is equivalent to value.

または-or- valuenull で、typeCodeEmptyString、または Object の場合は、null 参照 (Visual Basic の場合は Nothing)。A null reference (Nothing in Visual Basic), if value is null and typeCode is Empty, String, or Object.

例外

この変換はサポートされていません。This conversion is not supported.

または-or- valuenull であり、typeCode は値の型を指定します。value is null and typeCode specifies a value type.

または-or- valueIConvertible インターフェイスを実装していません。value does not implement the IConvertible interface.

valueprovider によって認識される typeCode 型の形式ではありません。value is not in a format for the typeCode type recognized by provider.

valuetypeCode 型の範囲外にある数値を表します。value represents a number that is out of the range of the typeCode type.

typeCode が無効です。typeCode is invalid.

次の例では、という名前のカスタム書式プロバイダーを定義します。InterceptProviderを示すときにそのGetFormatメソッドは呼び出され、を返します、 NumberFormatInfo 、FR-FR カルチャのとDateTimeFormatInfoEN-US カルチャの。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. この書式プロバイダーがすべての呼び出しで使用される、ChangeType(Object, TypeCode, IFormatProvider)メソッド。This format provider is used in all calls to the ChangeType(Object, TypeCode, IFormatProvider) method. 配列を作成し、DoubleDateTime値およびに繰り返しの呼び出しを行うChangeType(Object, TypeCode, IFormatProvider)の各値の各メンバーと、TypeCode列挙体。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. メソッドを使用する場合の例を示しています、IFormatProviderパラメーターの使用法も示しています。 および、providerカルチャの書式設定を実行するパラメーター。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).

注釈

ChangeType(Object, TypeCode, IFormatProvider) 指定されたオブジェクトを変換する汎用変換メソッドは、valueで指定された定義済みの型をtypeCodeします。ChangeType(Object, TypeCode, IFormatProvider) is a general-purpose conversion method that converts the object specified by value to a predefined type specified by typeCode. valueパラメーターは任意の型のオブジェクトであることができます。The value parameter can be an object of any type. 変換には、成功のvalue実装する必要があります、IConvertibleインターフェイス、メソッドは単に、適切な呼び出しをラップしますのでIConvertibleメソッド。For the conversion to succeed, value must implement the IConvertible interface, because the method simply wraps a call to an appropriate IConvertible method. メソッドは、そのへの変換も必要があります。valuetypeCodeサポートされます。The method also requires that conversion of value to typeCode be supported.

ChangeType(Object, TypeCode, IFormatProvider)メソッドへの変換をサポートしていませんvalueをカスタム型。The ChangeType(Object, TypeCode, IFormatProvider) method does not support the conversion of value to a custom type. このような変換を実行するのには、呼び出し、ChangeType(Object, Type, IFormatProvider)メソッド。To perform such a conversion, call the ChangeType(Object, Type, IFormatProvider) method.

providerパラメーターは、IFormatProvider変換のための書式設定情報を提供します。The provider parameter is an IFormatProvider implementation that supplies formatting information for the conversion. このパラメーターが使用されるかどうか、どのように、基になる依存IConvertible実装します。Whether and how this parameter is used depends on the underlying IConvertible implementation. 場合value基本データ型は、provider次の変換にのみ使用されます。If value is a base data type, provider is used only for the following conversions. 場合、 null IFormatProvider 、これらのメソッドに渡される引数、CultureInfoを現在のスレッド カルチャを表すオブジェクトを使用します。If a nullIFormatProvider argument is passed to these methods, the CultureInfo object that represents the current thread culture is used.

場合valueがアプリケーション定義の型の場合は、そのIConvertible実装を使用して、可能性があります、providerパラメーター。If value is an application-defined type, its IConvertible implementation may use the provider parameter.

適用対象