Control.OnTextChanged(EventArgs) 方法

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

引发 TextChanged 事件。

protected:
 virtual void OnTextChanged(EventArgs ^ e);

protected virtual void OnTextChanged (EventArgs e);

abstract member OnTextChanged : EventArgs -> unit
override this.OnTextChanged : EventArgs -> unit

Protected Overridable Sub OnTextChanged (e As EventArgs)

参数

e

EventArgs

包含事件数据的 EventArgs。

示例

下面的代码示例更改 ForeColor 显示货币数据的派生类的 TextBox 。 该示例将文本转换为十进制数，如果数字为负数，将 更改为 ForeColorColor.Red ;如果该数字为正数，则更改为 Color.Black 。 此示例要求具有派生自 TextBox 类的类。

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

注解

引发事件时，将通过委托调用事件处理程序。 有关详细信息，请参阅 处理和引发事件。

方法 OnTextChanged 还使派生类无需附加委托即可处理 事件。 这是在派生类中处理事件的首选技术。

继承者说明

在派生类中重写 OnTextChanged(EventArgs) 时，一定要调用基类的 OnTextChanged(EventArgs) 方法，以便已注册的委托对事件进行接收。

另请参阅

• TextChanged