Missing 类

public ref class Missing sealed

public ref class Missing sealed : System::Runtime::Serialization::ISerializable

public sealed class Missing

public sealed class Missing : System.Runtime.Serialization.ISerializable

[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public sealed class Missing : System.Runtime.Serialization.ISerializable

type Missing = class

type Missing = class
    interface ISerializable

[<System.Runtime.InteropServices.ComVisible(true)>]
[<System.Serializable>]
type Missing = class
    interface ISerializable

Public NotInheritable Class Missing

Public NotInheritable Class Missing
Implements ISerializable

继承

Object

Missing

属性

ComVisibleAttribute SerializableAttribute

实现

ISerializable

以下示例演示如何使用 Missing 对象通过反射调用具有默认参数的方法。

using System;
using System.Reflection;

[assembly:CLSCompliant(true)]

public class MissingClass
{
   public static void MethodWithDefault(int value = 33)
   {
      Console.WriteLine("value = {0}", value);
   } 
}

public class Example
{
   public static void Main()
   {
      // Invoke without reflection
      MissingClass.MethodWithDefault();
      
      // Invoke by using reflection.
      Type t = typeof(MissingClass);
      MethodInfo mi = t.GetMethod("MethodWithDefault");
      mi.Invoke(null, new object[] { Missing.Value });
   }
}
// The example displays the following output:
//       value = 33  
//       value = 33

Imports System.Reflection

<Assembly:CLSCompliant(True)>

Public Class MissingClass
   Public Shared Sub MethodWithDefault(Optional value As Integer = 33)
      Console.WriteLine("value = {0}", value)
   End Sub 
End Class   

Public Module Example
   Public Sub Main()
      ' Invoke without reflection.
      MissingClass.MethodWithDefault()
      
      ' Invoke by using reflection.
      Dim t As Type = GetType(MissingClass)
      Dim mi As MethodInfo = t.GetMethod("MethodWithDefault")
      mi.Invoke(Nothing, { Missing.Value })
   End Sub
End Module
' The example displays the following output:
'       value = 33 
'       value = 33

类 Missing 用于调用具有默认参数的方法，通常在使用反射时。

字段返回Value的 Missing只有一个 实例。

• DBNull