Nullable<T>.ToString 方法

public:
 override System::String ^ ToString();

public override string ToString();

public override string? ToString();

override this.ToString : unit -> string

Public Overrides Function ToString () As String

返回

如果 Nullable<T> 属性为 HasValue，则是当前 true 对象的值的文本表示形式；如果 HasValue 属性为 false，则是一个空字符串 ("")。

示例

下面的代码示例显示当前 Nullable<T> 对象的值。

// This code example demonstrates the
// Nullable<T>.ToString method.

using System;

class Sample
{
    public static void Main()
    {
    DateTime? nullableDate;

// Display the current date and time.
    nullableDate = DateTime.Now;
    Display("1)", nullableDate);

// Assign null (Nothing in Visual Basic) to nullableDate, then
// display its value.
    nullableDate = null;
    Display("2)", nullableDate);
    }

// Display the text representation of a nullable DateTime.
    public static void Display(string title, DateTime? dspDT)
    {
    string msg = dspDT.ToString();

    Console.Write("{0} ", title);
    if (String.IsNullOrEmpty(msg))
        Console.WriteLine("The nullable DateTime has no defined value.");
    else
        Console.WriteLine("The current date and time is {0}.", msg);
    }
}

/*
This code example produces the following results:

1) The current date and time is 4/19/2005 8:28:14 PM.
2) The nullable DateTime has no defined value.

*/

// This code example demonstrates the
// Nullable<T>.ToString method.
open System

// Display the text representation of a nullable DateTime.
let display title dspDT =
    let msg = dspDT.ToString()

    printf $"{title} "
    if String.IsNullOrEmpty msg then
        printfn "The nullable DateTime has no defined value."
    else
        printfn $"The current date and time is {msg}."

[<EntryPoint>]
let main _ =
    // Display the current date and time.
    let nullableDate = Nullable DateTime.Now
    display "1)" nullableDate

    // Assign null (Nothing in Visual Basic) to nullableDate, then
    // display its value.
    let nullableDate = Nullable()
    display "2)" nullableDate
    0

// This code example produces the following results:
//     1) The current date and time is 4/19/2005 8:28:14 PM.
//     2) The nullable DateTime has no defined value.

' This code example demonstrates the 
' Nullable<T>.ToString method.

Class Sample
    Public Shared Sub Main() 
        Dim nullableDate As Nullable(Of DateTime)
    ' Display the current date and time.
        nullableDate = DateTime.Now
        Display("1)", nullableDate)
        
    ' Assign null (Nothing in Visual Basic) to nullableDate, then 
    ' display its value.
        nullableDate = Nothing
        Display("2)", nullableDate)
    End Sub

    '  Display the text representation of a nullable DateTime.
    Public Shared Sub Display(ByVal title As String, _
                              ByVal dspDT As Nullable(Of DateTime))
        Dim msg As String = dspDT.ToString()

        Console.Write("{0} ", title)
        If String.IsNullOrEmpty(msg) Then
            Console.WriteLine("The nullable DateTime has no defined value.")
        Else
            Console.WriteLine("The current date and time is {0}.", msg)
        End If
    End Sub
End Class

'This code example produces the following results:
'
'1) The current date and time is 4/19/2005 8:28:14 PM.
'2) The nullable DateTime has no defined value.
'

注解

属性 ToString 返回通过调用 ToString 属性返回的 对象的 属性生成的 Value 字符串。