ConditionalWeakTable<TKey,TValue>.CreateValueCallback 代理人

定義

ConditionalWeakTable<TKey,TValue> オブジェクトにキー/値ペアの一部として追加する既定値以外の値を作成するメソッドを表します。Represents a method that creates a non-default value to add as part of a key/value pair to a ConditionalWeakTable<TKey,TValue> object.

public:  where TKey : class where TValue : classdelegate TValue ConditionalWeakTable<TKey, TValue>::CreateValueCallback(TKey key);
public delegate TValue ConditionalWeakTable<TKey,TValue>.CreateValueCallback(TKey key) where TKey : class where TValue : class;
type ConditionalWeakTable<'Key, 'Value (requires 'Key : null and 'Value : null)>.CreateValueCallback = delegate of 'Key -> 'Value
Public Delegate Function ConditionalWeakTable(Of TKey, TValue).CreateValueCallback(key As TKey) As TValue 

型パラメーター

TKey
TValue

パラメーター

key

作成する値に属しているキー。The key that belongs to the value to create.

戻り値

TValue

指定したキーにアタッチする値を表す、参照型のインスタンス。An instance of a reference type that represents the value to attach to the specified key.

継承
ConditionalWeakTable<TKey,TValue>.CreateValueCallback

次の例では、MainClass クラスと MainInfo クラスを定義します。The following example defines a MainClass class and a MainInfo class. MainInfo MainClass インスタンスに関する情報を提供します。MainInfo provides information about the MainClass instance. また、ConditionalWeakTable<TKey,TValue>.CreateValueCallback デリゲートに割り当てて GetValue メソッドに渡すことができる静的 (Visual Basic でShared) CreateAttachedValue メソッドを定義します。It also defines a static (Shared in Visual Basic) CreateAttachedValue method that can be assigned to the ConditionalWeakTable<TKey,TValue>.CreateValueCallback delegate and passed to the GetValue method. この例では、GetValue メソッドを呼び出して、MainClass オブジェクトとそれに対応する MainInfo オブジェクトを ConditionalWeakTable<TKey,TValue> テーブルに追加します。The example calls the GetValue method to add a MainClass object and its corresponding MainInfo object to a ConditionalWeakTable<TKey,TValue> table. また、この例では、AddGetOrCreateValue メソッドを呼び出して、キーと値のペアをテーブルに追加する方法と、既存のキーに属する値を取得するための TryGetValue メソッドの呼び出しについても説明しています。The example also illustrates calls to the Add and GetOrCreateValue methods to add key/value pairs to the table, and a call to the TryGetValue method to retrieve the value that belongs to an existing key.

using System;
using System.Reflection;
using System.Runtime.CompilerServices;

public class Example
{
   string Name; 
   
   public Example(string name)
   {
      this.Name = name;
   }
   
   public override string ToString()
   {
      return this.Name;
   }
}

// Define a class to contain information about each Example instance.
public class ExampleInfo
{
   public string Name;
   public int Methods;
   public int Properties;
   
   public override string ToString()
   {
      return String.Format("{0}: {1} Methods, {2} Properties", 
                           this.Name, this.Methods, this.Properties);
   }
}

public class ExampleTest
{
   private static BindingFlags flags = BindingFlags.Public | BindingFlags.Instance;

   public static void Main()
   {
      Example ex1 = new Example("ex1");
      Example ex2 = new Example("ex2");
      Example ex3 = new Example("ex3");
      
      ExampleInfo exInfo1 = new ExampleInfo(); 
      exInfo1.Name = ex1.ToString();
      exInfo1.Methods = ex1.GetType().GetMethods(flags).Length;
      exInfo1.Properties = ex1.GetType().GetProperties(flags).Length;
      
      ExampleInfo exInfo3 = new ExampleInfo(); 
      exInfo3.Name = ex3.ToString();
      exInfo3.Methods = ex3.GetType().GetMethods(flags).Length;
      exInfo3.Properties = ex3.GetType().GetProperties(flags).Length;

      var attached = new ConditionalWeakTable<Example, ExampleInfo>();
      ExampleInfo value = null;

      // Attach a property to ex1 using the Add method, then retrieve it.
      attached.Add(ex1, exInfo1);
      if (attached.TryGetValue(ex1, out value))
         Console.WriteLine("{0}, {1}", ex1, value);
      else
         Console.WriteLine("{0} does not have an attached property.", ex1);

      // Attempt to retrieve the value attached to ex2.
      value = attached.GetValue(ex2, ExampleTest.CreateAttachedValue);      
      if (attached.TryGetValue(ex2, out value))
         Console.WriteLine("{0}, {1}", ex2, value);
      else 
         Console.WriteLine("{0} does not have an attached property.", ex2);
      
      // Attempt to retrieve the value attached to ex3.
      value = attached.GetOrCreateValue(ex3);
      Console.WriteLine("{0}, {1}", ex3, value);
   }

   public static ExampleInfo CreateAttachedValue(Example ex)
   {
      ExampleInfo info = new ExampleInfo();
      info.Name = ex.ToString();
      info.Methods = ex.GetType().GetMethods(flags).Length;
      info.Properties = ex.GetType().GetProperties(flags).Length;
      return info;
   }
}
// The example displays the following output:
//       ex1, ex1: 4 Methods, 0 Properties
//       ex2, ex2: 4 Methods, 0 Properties
//       ex3, : 0 Methods, 0 Properties
Imports System.Reflection
Imports System.Runtime.CompilerServices

Public Class Example
   Public Name As String
   
   Public Sub New(name As String)
      Me.Name = name
   End Sub
   
   Public Overrides Function ToString() As String
      Return Me.Name
   End Function
End Class

' Define a class to contain information about each Example instance.
Public Class ExampleInfo
   Public Name As String
   Public Methods As Integer
   Public Properties As Integer
   
   Public Overrides Function ToString() As String
      Return String.Format("{0}: {1} Methods, {2} Properties", _
                           Me.Name, Me.Methods, Me.Properties)
   End Function
End Class

Module TestExample

   Private flags As BindingFlags = BindingFlags.Public Or BindingFlags.Instance

   Public Sub Main()
      Dim ex1 As New Example("ex1")
      Dim ex2 As New Example("ex2")
      Dim ex3 As New Example("ex3")
      
      Dim exInfo1 As New ExampleInfo() 
      exInfo1.Name = ex1.ToString()
      exInfo1.Methods = ex1.GetType().GetMethods(flags).Count
      exInfo1.Properties = ex1.GetType().GetProperties(flags).Count
      
      Dim exInfo3 As New ExampleInfo() 
      exInfo3.Name = ex3.ToString()
      exInfo3.Methods = ex3.GetType().GetMethods(flags).Count
      exInfo3.Properties = ex3.GetType().GetProperties(flags).Count

      Dim attached As New ConditionalWeakTable(Of Example, ExampleInfo)
      Dim value As ExampleInfo = Nothing

      ' Attach a property to ex1 using the Add method, then retrieve it.
      attached.Add(ex1, exInfo1)
      If attached.TryGetValue(ex1, value) Then
         Console.WriteLine("{0}, {1}", ex1, value)
      Else
         Console.WriteLine("{0} does not have an attached property.", ex1)
      End If

      ' Attempt to retrieve the value attached to ex2.
      value = attached.GetValue(ex2, AddressOf TestExample.CreateAttachedValue)      
      If attached.TryGetValue(ex2, value) Then
         Console.WriteLine("{0}, {1}", ex2, value)
      Else 
         Console.WriteLine("{0} does not have an attached property.", ex2)
      End If
      
      ' Atttempt to retrieve the value attached to ex3.
      value = attached.GetOrCreateValue(ex3)
      Console.WriteLine("{0}, {1}", ex3, value)
   End Sub
   
   Public Function CreateAttachedValue(ex As Example) As ExampleInfo
      Dim info As New ExampleInfo()
      info.Name = ex.ToString()
      info.Methods = ex.GetType().GetMethods(flags).Count
      info.Properties = ex.GetType().GetProperties(flags).Count
      Return info
   End Function
End Module
' The example displays the following output:
'       ex1, ex1: 4 Methods, 0 Properties
'       ex2, ex2: 4 Methods, 0 Properties
'       ex3, : 0 Methods, 0 Properties

注釈

ConditionalWeakTable<TKey,TValue>.CreateValueCallback デリゲートは、メソッドに渡されたキーが ConditionalWeakTable<TKey,TValue> オブジェクトに見つからない場合に、ConditionalWeakTable<TKey,TValue>.GetValue メソッドによって呼び出されるコールバックメソッドをカプセル化します。The ConditionalWeakTable<TKey,TValue>.CreateValueCallback delegate encapsulates a callback method that is invoked by the ConditionalWeakTable<TKey,TValue>.GetValue method when the key passed to the method is not found in the ConditionalWeakTable<TKey,TValue> object. GetValue メソッドは、プロパティ値を動的にアタッチするマネージオブジェクトを表すキーをコールバックメソッドに渡します。The GetValue method passes the callback method the key that represents a managed object to which a property value is to be dynamically attached. メソッドは、プロパティ値を呼び出し元に返す役割を担います。その結果、キーと値のペアがテーブルに追加されます。The method is responsible for returning the property value to its caller, which, in turn, adds the key/value pair to the table.

ConditionalWeakTable<TKey,TValue>.CreateValueCallback メソッドは、指定されたキーにアタッチできる参照型のインスタンスを返すために使用されます。The ConditionalWeakTable<TKey,TValue>.CreateValueCallback method is used to return an instance of a reference type that can be attached to the specified key. これにより、既定値以外の値を使用してインスタンスを初期化できるようになります。It enables that instance to be initialized using non-default values. キーがテーブルに見つからない場合、ConditionalWeakTable<TKey,TValue>.GetOrCreateValue メソッドは、値が既定値を使用して初期化されるキーと値のペアを追加します。If the key is not found in the table, the ConditionalWeakTable<TKey,TValue>.GetOrCreateValue method adds a key/value pair in which the value is initialized using default values.

拡張メソッド

GetMethodInfo(Delegate)

指定したデリゲートによって表されるメソッドを表すオブジェクトを取得します。Gets an object that represents the method represented by the specified delegate.

適用対象

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