Control.OnContextMenuChanged(EventArgs) 方法

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

來源:

Control.cs

警告

ContextMenu is provided for binary compatibility with .NET Framework and is not intended to be used directly from your code. Use ContextMenuStrip instead.

引發 ContextMenuChanged 事件。

protected:
 virtual void OnContextMenuChanged(EventArgs ^ e);

[System.ComponentModel.Browsable(false)]
[System.Obsolete("`ContextMenu` is provided for binary compatibility with .NET Framework and is not intended to be used directly from your code. Use `ContextMenuStrip` instead.", false, DiagnosticId="WFDEV006", UrlFormat="https://aka.ms/winforms-warnings/{0}")]
protected virtual void OnContextMenuChanged(EventArgs e);

[<System.ComponentModel.Browsable(false)>]
[<System.Obsolete("`ContextMenu` is provided for binary compatibility with .NET Framework and is not intended to be used directly from your code. Use `ContextMenuStrip` instead.", false, DiagnosticId="WFDEV006", UrlFormat="https://aka.ms/winforms-warnings/{0}")>]
abstract member OnContextMenuChanged : EventArgs -> unit
override this.OnContextMenuChanged : EventArgs -> unit

Protected Overridable Sub OnContextMenuChanged (e As EventArgs)

參數

e

EventArgs

一個 EventArgs 包含事件資料的 。

屬性

BrowsableAttribute ObsoleteAttribute

範例

以下程式碼範例是一個事件引發方法，當屬性值改變時 Text 會執行。 該Control類別有多個名為 PropertyNameChanged 的命名模式On方法，當 PropertyName 值改變時會觸發相應的 PropertyNameChanged 事件（PropertyName 代表對應屬性的名稱）。

以下程式碼範例變更ForeColorTextBox了顯示貨幣資料的衍生類別。 範例將文字轉換為十進位數字，若數字為負數則將 轉換為 ForeColorColor.Red ，若數字為正數則改為 Color.Black 。 這個例子要求你有一個從該 TextBox 類別衍生出來的類別。

protected:
   virtual void OnTextChanged( System::EventArgs^ e ) override
   {
      try
      {
         // Convert the text to a Double and determine
         // if it is a negative number.
         if ( Double::Parse( this->Text ) < 0 )
         {
            // If the number is negative, display it in Red.
            this->ForeColor = Color::Red;
         }
         else
         {
            // If the number is not negative, display it in Black.
            this->ForeColor = Color::Black;
         }
      }
      catch ( Exception^ ) 
      {
         // If there is an error, display the
         // text using the system colors.
         this->ForeColor = SystemColors::ControlText;
      }

      TextBox::OnTextChanged( e );
   }

protected override void OnTextChanged(System.EventArgs e)
{
   try
   {
      // Convert the text to a Double and determine
      // if it is a negative number.
      if(double.Parse(this.Text) < 0)
      {
         // If the number is negative, display it in Red.
         this.ForeColor = Color.Red;
      }
      else
      {
         // If the number is not negative, display it in Black.
         this.ForeColor = Color.Black;
      }
   }
   catch
   {
      // If there is an error, display the 
      // text using the system colors.
      this.ForeColor = SystemColors.ControlText;
   }
   
   base.OnTextChanged(e);
}

Protected Overrides Sub OnTextChanged(e As System.EventArgs)
   Try
      ' Convert the text to a Double and determine
      ' if it is a negative number.
      If Double.Parse(Me.Text) < 0 Then
         ' If the number is negative, display it in Red.
         Me.ForeColor = Color.Red
      Else
         ' If the number is not negative, display it in Black.
         Me.ForeColor = Color.Black
      End If
   Catch
      ' If there is an error, display the
      ' text using the system colors.
      Me.ForeColor = SystemColors.ControlText
   End Try

   MyBase.OnTextChanged(e)
End Sub

備註

發起事件會透過代理呼叫事件處理者。 欲了解更多資訊，請參閱 處理與提升事件。

此 OnContextMenuChanged 方法也允許衍生類別在不附加代理的情況下處理事件。 這是在衍生類別中處理事件的首選技術。

給繼承者的注意事項

在導出類別中覆寫 OnContextMenuChanged(EventArgs) 時，務必呼叫基底類別的方法 OnContextMenuChanged(EventArgs) ，讓註冊代理接收事件。

另請參閱

• ContextMenuChanged
• ContextMenu