Nullable<T>.GetValueOrDefault Método

Definição

Recupera o valor do objeto Nullable<T> atual ou um valor padrão.Retrieves the value of the current Nullable<T> object, or a default value.

Sobrecargas

GetValueOrDefault()

Recupera o valor do objeto Nullable<T> atual ou o valor padrão do tipo subjacente.Retrieves the value of the current Nullable<T> object, or the default value of the underlying type.

GetValueOrDefault(T)

Recupera o valor do objeto Nullable<T> atual ou o valor padrão especificado.Retrieves the value of the current Nullable<T> object, or the specified default value.

Exemplos

O exemplo de código a seguir recupera o valor de um Nullable<T> objeto se esse valor for definido; caso contrário, ele recuperará o valor padrão ou um valor padrão específico.The following code example retrieves the value of a Nullable<T> object if that value is defined; otherwise, it retrieves the default value or a specific default value.

// This code example demonstrates the
// Nullable<T>.GetValueOrDefault methods.

using System;

class Sample
{
    public static void Main()
    {
    float? mySingle = 12.34f;
    float? yourSingle = -1.0f;

   Console.WriteLine("*** Display a value or the default value ***\n");
// Display the values of mySingle and yourSingle.

    Display("A1", mySingle, yourSingle);

// Assign the value of mySingle to yourSingle, then display the values
// of mySingle and yourSingle. The yourSingle variable is assigned the
// value 12.34 because mySingle has a value.

    yourSingle = mySingle.GetValueOrDefault();
    Display("A2", mySingle, yourSingle);

// Assign null (Nothing in Visual Basic) to mySingle, which means no value is
// defined for mySingle. Then assign the value of mySingle to yourSingle and
// display the values of both variables. The default value of all binary zeroes
// is assigned to yourSingle because mySingle has no value.

    mySingle = null;
    yourSingle = mySingle.GetValueOrDefault();
    Display("A3", mySingle, yourSingle);

// Reassign the original values of mySingle and yourSingle.
    mySingle = 12.34f;
    yourSingle = -1.0f;

    Console.Write("\n*** Display a value or the ");
    Console.WriteLine("specified default value ***\n");

// Display the values of mySingle and yourSingle.
    Display("B1", mySingle, yourSingle);

// Assign the value of mySingle to yourSingle, then display the values
// of mySingle and yourSingle. The yourSingle variable is assigned the
// value 12.34 because mySingle has a value.

    yourSingle = mySingle.GetValueOrDefault(-222.22f);
    Display("B2", mySingle, yourSingle);

// Assign null (Nothing in Visual Basic) to mySingle, which means no value is
// defined for mySingle. Then assign the value of mySingle to yourSingle and
// display the values of both variables. The specified default value of -333.33
// is assigned to yourSingle because mySingle has no value.

    mySingle = null;
    yourSingle = mySingle.GetValueOrDefault(-333.33f);
    Display("B3", mySingle, yourSingle);
    }

// Display the values of two nullable of System.Single structures.
// The Console.WriteLine method automatically calls the ToString methods of
// each input argument to display its values. If no value is defined for a
// nullable type, the ToString method for that argument returns the empty
// string ("").
    public static void Display(string title, float? dspMySingle, float? dspYourSingle)
    {
    Console.WriteLine("{0}) mySingle = [{1}], yourSingle = [{2}]",
                      title, dspMySingle, dspYourSingle);
    }
}

/*
This code example produces the following results:

A1) mySingle = [12.34], yourSingle = [-1]
A2) mySingle = [12.34], yourSingle = [12.34]
A3) mySingle = [], yourSingle = [0]

*** Display a value or the specified default value ***

B1) mySingle = [12.34], yourSingle = [-1]
B2) mySingle = [12.34], yourSingle = [12.34]
B3) mySingle = [], yourSingle = [-333.33]

*/
' This code example demonstrates the 
' Nullable(Of T).GetValueOrDefault methods.

Class Sample
    Public Shared Sub Main() 
        Dim mySingle As Nullable(Of System.Single) = 12.34F 
        Dim yourSingle As Nullable(Of System.Single) = - 1.0F 
        
        Console.WriteLine("*** Display a value or the default value ***" & vbCrLf)
    ' Display the values of mySingle and yourSingle.
        Display("A1", mySingle, yourSingle)
        
    ' Assign the value of mySingle to yourSingle, then display the values 
    ' of mySingle and yourSingle. The yourSingle variable is assigned the 
    ' value 12.34 because mySingle has a value.
        yourSingle = mySingle.GetValueOrDefault()
        Display("A2", mySingle, yourSingle)
        
    ' Assign null (Nothing in Visual Basic) to mySingle, which means no value is
    ' defined for mySingle. Then assign the value of mySingle to yourSingle and
    ' display the values of both variables. The default value of all binary zeroes 
    ' is assigned to yourSingle because mySingle has no value.
        mySingle = Nothing
        yourSingle = mySingle.GetValueOrDefault()
        Display("A3", mySingle, yourSingle)
        
    ' Reassign the original values of mySingle and yourSingle.
        mySingle = 12.34F
        yourSingle = - 1.0F
        
        Console.Write(vbCrLf & "*** Display a value or the ")
        Console.WriteLine("specified default value ***" & vbCrLf)
        
    ' Display the values of mySingle and yourSingle.
        Display("B1", mySingle, yourSingle)
        
    ' Assign the value of mySingle to yourSingle, then display the values 
    ' of mySingle and yourSingle. The yourSingle variable is assigned the 
    ' value 12.34 because mySingle has a value.
        yourSingle = mySingle.GetValueOrDefault(- 222.22F)
        Display("B2", mySingle, yourSingle)
        
    ' Assign null (Nothing in Visual Basic) to mySingle, which means no value is
    ' defined for mySingle. Then assign the value of mySingle to yourSingle and
    ' display the values of both variables. The specified default value of -333.33
    ' is assigned to yourSingle because mySingle has no value.
        mySingle = Nothing
        yourSingle = mySingle.GetValueOrDefault(- 333.33F)
        Display("B3", mySingle, yourSingle)
    
    End Sub
     
    
    ' Display the values of two nullable of System.Single structures.
    ' The Console.WriteLine method automatically calls the ToString methods of 
    ' each input argument to display its values. If no value is defined for a
    ' nullable type, the ToString method for that argument returns the empty
    ' string ("").

    Public Shared Sub Display(ByVal title As String, _
                              ByVal dspMySingle As Nullable(Of System.Single), _
                              ByVal dspYourSingle As Nullable(Of System.Single))
        If (True) Then
            Console.WriteLine("{0}) mySingle = [{1}], yourSingle = [{2}]", _
                               title, dspMySingle, dspYourSingle)
        End If
    End Sub
End Class

'
'This code example produces the following results:
'
'A1) mySingle = [12.34], yourSingle = [-1]
'A2) mySingle = [12.34], yourSingle = [12.34]
'A3) mySingle = [], yourSingle = [0]
'
'*** Display a value or the specified default value ***
'
'B1) mySingle = [12.34], yourSingle = [-1]
'B2) mySingle = [12.34], yourSingle = [12.34]
'B3) mySingle = [], yourSingle = [-333.33]
'

GetValueOrDefault()

Recupera o valor do objeto Nullable<T> atual ou o valor padrão do tipo subjacente.Retrieves the value of the current Nullable<T> object, or the default value of the underlying type.

public:
 T GetValueOrDefault();
public T GetValueOrDefault ();
member this.GetValueOrDefault : unit -> 'T
Public Function GetValueOrDefault () As T

Retornos

T

O valor da propriedade Value se a propriedade HasValue for true; caso contrário, o valor padrão do tipo subjacente.The value of the Value property if the HasValue property is true; otherwise, the default value of the underlying type.

Comentários

O GetValueOrDefault método retorna um valor mesmo se a HasValue propriedade for false (ao contrário da Value propriedade, que gera uma exceção).The GetValueOrDefault method returns a value even if the HasValue property is false (unlike the Value property, which throws an exception). Se a HasValue propriedade for false , o método retornará o valor padrão do tipo subjacente.If the HasValue property is false, the method returns the default value of the underlying type.

Confira também

Aplica-se a

GetValueOrDefault(T)

Recupera o valor do objeto Nullable<T> atual ou o valor padrão especificado.Retrieves the value of the current Nullable<T> object, or the specified default value.

public:
 T GetValueOrDefault(T defaultValue);
public T GetValueOrDefault (T defaultValue);
member this.GetValueOrDefault : 'T -> 'T
Public Function GetValueOrDefault (defaultValue As T) As T

Parâmetros

defaultValue
T

Um valor a ser retornado se a propriedade HasValue for false.A value to return if the HasValue property is false.

Retornos

T

O valor da propriedade Value se a propriedade HasValue for true; caso contrário, o parâmetro defaultValue.The value of the Value property if the HasValue property is true; otherwise, the defaultValue parameter.

Comentários

O GetValueOrDefault método retorna um valor mesmo se a HasValue propriedade for false (ao contrário da Value propriedade, que gera uma exceção).The GetValueOrDefault method returns a value even if the HasValue property is false (unlike the Value property, which throws an exception).

Confira também

Aplica-se a