Nullable.GetUnderlyingType(Type) Metode

Definisi

Ruang nama:

System

Rakitan:

netstandard.dll, System.Runtime.dll

Sumber:

Nullable.cs

Mengembalikan argumen jenis yang mendasar dari jenis nullable yang ditentukan.

public:
 static Type ^ GetUnderlyingType(Type ^ nullableType);

public static Type? GetUnderlyingType(Type nullableType);

static member GetUnderlyingType : Type -> Type

Public Shared Function GetUnderlyingType (nullableType As Type) As Type

Parameter

nullableType

Type

Objek Type yang menjelaskan jenis generik tertutup yang dapat diubah ke null.

Mengembalikan

Type

Argumen jenis nullableType parameter, jika nullableType parameter adalah jenis nullable generik tertutup; jika tidak, null.

Pengecualian

ArgumentNullException

nullableType adalah null.

Contoh

Contoh kode berikut mendefinisikan metode yang nilai pengembaliannya adalah jenis Nullable<T>Int32. Contoh kode menggunakan GetUnderlyingType metode untuk menampilkan argumen jenis nilai yang dikembalikan.

// This code example demonstrates the
// Nullable.GetUnderlyingType() method.

using System;
using System.Reflection;

class Sample
{
// Declare a type named Example.
// The MyMethod member of Example returns a Nullable of Int32.

    public class Example
    {
        public int? MyMethod()
        {
        return 0;
        }
    }

/*
   Use reflection to obtain a Type object for the Example type.
   Use the Type object to obtain a MethodInfo object for the MyMethod method.
   Use the MethodInfo object to obtain the type of the return value of
     MyMethod, which is Nullable of Int32.
   Use the GetUnderlyingType method to obtain the type argument of the
     return value type, which is Int32.
*/
    public static void Main()
    {
        Type t = typeof(Example);
        MethodInfo mi = t.GetMethod("MyMethod");
        Type retval = mi.ReturnType;
        Console.WriteLine("Return value type ... {0}", retval);
        Type answer = Nullable.GetUnderlyingType(retval);
        Console.WriteLine("Underlying type ..... {0}", answer);
    }
}
/*
This code example produces the following results:

Return value type ... System.Nullable`1[System.Int32]
Underlying type ..... System.Int32

*/

// This code example demonstrates the
// Nullable.GetUnderlyingType() method.
open System

// Declare a type named Example.
// The MyMethod member of Example returns a Nullable of Int32.

type Example() =
    member _.MyMethod() =
        Nullable 0

(*
   Use reflection to obtain a Type object for the Example type.
   Use the Type object to obtain a MethodInfo object for the MyMethod method.
   Use the MethodInfo object to obtain the type of the return value of
     MyMethod, which is Nullable of Int32.
   Use the GetUnderlyingType method to obtain the type argument of the
     return value type, which is Int32.
*)
let t = typeof<Example>
let mi = t.GetMethod "MyMethod"
let retval = mi.ReturnType
printfn $"Return value type ... {retval}"
let answer = Nullable.GetUnderlyingType retval
printfn $"Underlying type ..... {answer}"

// This code example produces the following results:
//     Return value type ... System.Nullable`1[System.Int32]
//     Underlying type ..... System.Int32

' This code example demonstrates the 
' Nullable.GetUnderlyingType() method.

Imports System.Reflection

Class Sample
    ' Declare a type named Example. 
    ' The MyMethod member of Example returns a Nullable of Int32.
    
    Public Class Example
        Public Function MyMethod() As Nullable(Of Integer)
            Return 0
        End Function
    End Class
    
' 
'   Use reflection to obtain a Type object for the Example type.
'   Use the Type object to obtain a MethodInfo object for the MyMethod method.
'   Use the MethodInfo object to obtain the type of the return value of 
'     MyMethod, which is Nullable of Int32.
'   Use the GetUnderlyingType method to obtain the type argument of the 
'     return value type, which is Int32.
'
    Public Shared Sub Main() 
        Dim t As Type = GetType(Example)
        Dim mi As MethodInfo = t.GetMethod("MyMethod")
        Dim retval As Type = mi.ReturnType
        Console.WriteLine("Return value type ... {0}", retval)
        Dim answer As Type = Nullable.GetUnderlyingType(retval)
        Console.WriteLine("Underlying type ..... {0}", answer)
    
    End Sub
End Class
'
'This code example produces the following results:
'
'Return value type ... System.Nullable`1[System.Int32]
'Underlying type ..... System.Int32
'

Keterangan

Definisi jenis generik adalah deklarasi jenis, seperti Nullable<T>, yang berisi daftar parameter jenis, dan daftar parameter jenis mendeklarasikan satu atau beberapa parameter jenis. Jenis generik tertutup adalah deklarasi jenis di mana jenis tertentu ditentukan untuk parameter jenis.

Misalnya, jika parameter nullableType adalah jenis Nullable<Int32> di C# (Nullable(Of Int32) dalam Visual Basic), nilai yang dikembalikan adalah jenis Int32 (yaitu, argumen jenis jenis generik tertutup).