Nullable<T>.GetValueOrDefault Metoda

Definicja

Przestrzeń nazw:

System

Zestaw:

System.Runtime.dll

Pobiera wartość bieżącego Nullable<T> obiektu lub wartość domyślną.

Przeciążenia

GetValueOrDefault()	Pobiera wartość bieżącego Nullable<T> obiektu lub wartość domyślną typu bazowego.
GetValueOrDefault(T)	Pobiera wartość bieżącego Nullable<T> obiektu lub określoną wartość domyślną.

Przykłady

Poniższy przykład kodu pobiera wartość Nullable<T> obiektu, jeśli ta wartość jest zdefiniowana. W przeciwnym razie pobiera wartość domyślną lub określoną wartość domyślną.

// 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<T>.GetValueOrDefault methods.
open System

// Display the values of two nullable of System.Single structures.
// The printfn string interpolation 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 ("").
let display title dspMySingle dspYourSingle =
    printfn $"{title}) mySingle = [{dspMySingle}], yourSingle = [{dspYourSingle}]"

let mySingle = Nullable 12.34f
let yourSingle = Nullable -1f

[<EntryPoint>]
let main _ =
    printfn "*** Display a value or the default value ***\n"
    // Display the values of mySingle and yourSingle.

    display "A1" mySingle yourSingle

    // Shadow 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.

    let yourSingle = mySingle.GetValueOrDefault()
    display "A2" mySingle yourSingle

    // Shadow 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.

    let mySingle = Nullable()
    let yourSingle = mySingle.GetValueOrDefault()
    display "A3" mySingle yourSingle

    // Shadow the original values of mySingle and yourSingle.
    let mySingle = Nullable 12.34f
    let yourSingle = Nullable -1.0f

    printf "\n*** Display a value or the "
    printfn "specified default value ***\n"

    // Display the values of mySingle and yourSingle.
    display "B1" mySingle yourSingle

    // Shadow 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.

    let yourSingle = mySingle.GetValueOrDefault -222.22f
    display "B2" mySingle yourSingle

    // Shadow null (Nothing in Visual Basic) to mySingle, which means no value is
    // defined for mySingle. Then shadow 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.

    let mySingle = Nullable()
    let yourSingle = mySingle.GetValueOrDefault -333.33f
    display "B3" mySingle yourSingle
    0

// 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()

Źródło:

Nullable.cs

Pobiera wartość bieżącego Nullable<T> obiektu lub wartość domyślną typu bazowego.

public:
 T GetValueOrDefault();

public readonly T GetValueOrDefault ();

member this.GetValueOrDefault : unit -> 'T

Public Function GetValueOrDefault () As T

Zwraca

T

Wartość Value właściwości , jeśli HasValue właściwość ma truewartość ; w przeciwnym razie wartość domyślna typu bazowego.

Uwagi

Metoda GetValueOrDefault zwraca wartość, nawet jeśli HasValue właściwość jest false (w przeciwieństwie do Value właściwości, która zgłasza wyjątek). HasValue Jeśli właściwość to false, metoda zwraca wartość domyślną typu bazowego.

Zobacz też

• GetValueOrDefault(T)

GetValueOrDefault(T)

Źródło:

Nullable.cs

Pobiera wartość bieżącego Nullable<T> obiektu lub określoną wartość domyślną.

public:
 T GetValueOrDefault(T defaultValue);

public readonly T GetValueOrDefault (T defaultValue);

member this.GetValueOrDefault : 'T -> 'T

Public Function GetValueOrDefault (defaultValue As T) As T

Parametry

defaultValue

T

Wartość, która ma być zwracana, jeśli HasValue właściwość to false.

Zwraca

T

Wartość Value właściwości , jeśli HasValue właściwość to true; w przeciwnym razie defaultValue parametr.

Uwagi

Metoda GetValueOrDefault zwraca wartość, nawet jeśli HasValue właściwość jest false (w przeciwieństwie do Value właściwości, która zgłasza wyjątek).

Zobacz też

• GetValueOrDefault()