ToolStripComboBox.DropDown 事件


發生於顯示 ToolStripComboBox 的下拉部分時。Occurs when the drop-down portion of a ToolStripComboBox is shown.

 event EventHandler ^ DropDown;
public event EventHandler DropDown;
member this.DropDown : EventHandler 
Public Custom Event DropDown As EventHandler 


下列程式碼範例示範如何使用這個成員。The following code example demonstrates the use of this member. 在此範例中,事件處理常式會報告 DropDown 事件的發生。In the example, an event handler reports on the occurrence of the DropDown event. 此報表可協助您瞭解事件發生的時間,並可協助您進行調試。This report helps you to learn when the event occurs and can assist you in debugging. 若要報告多個事件或經常發生的事件,請考慮使用 Console.WriteLine 取代 MessageBox.Show,或將訊息附加到多行 TextBoxTo report on multiple events or on events that occur frequently, consider replacing MessageBox.Show with Console.WriteLine or appending the message to a multiline TextBox.

若要執行範例程式碼,請將它貼入專案,其中包含名為 ToolStripComboBox1ToolStripComboBox 類型的實例。To run the example code, paste it into a project that contains an instance of type ToolStripComboBox named ToolStripComboBox1. 然後確定事件處理常式與 DropDown 事件相關聯。Then ensure that the event handler is associated with the DropDown event.

private void ToolStripComboBox1_DropDown(Object sender, EventArgs e) {

   MessageBox.Show("You are in the ToolStripComboBox.DropDown event.");
Private Sub ToolStripComboBox1_DropDown(sender as Object, e as EventArgs) _ 
     Handles ToolStripComboBox1.DropDown

   MessageBox.Show("You are in the ToolStripComboBox.DropDown event.")

End Sub


如需事件處理常式委派的詳細資訊,請參閱處理和引發事件For more information about event-handler delegates, see Handling and Raising Events.