DateTimePicker.DropDown 事件

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

当显示下拉日历时发生。

public:
 event EventHandler ^ DropDown;

public event EventHandler? DropDown;

member this.DropDown : EventHandler 

Public Custom Event DropDown As EventHandler 

事件类型

EventHandler

示例

下面的代码示例演示如何使用 MinDateTime 和 MaxDateTime 字段处理 DropDown 的 DateTimePicker 事件。 若要运行此示例，请将以下代码粘贴到包含 DateTimePicker 名为 DateTimePicker1的窗体中。

// When the calendar drops down, display a MessageBox indicating 
// that DateTimePicker will not accept dates before MinDateTime or 
// after MaxDateTime. Use a StringBuilder object to build the string
// for efficiency.
void DateTimePicker1_DropDown( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
   System::Text::StringBuilder^ messageBuilder = gcnew System::Text::StringBuilder;
   messageBuilder->Append( "Choose a date after: " );
   messageBuilder->Append( DateTimePicker::MinDateTime.ToShortDateString() );
   messageBuilder->Append( " and a date before: " );
   messageBuilder->Append( DateTimePicker::MaxDateTime.ToShortDateString() );
   MessageBox::Show( messageBuilder->ToString() );
}

// When the calendar drops down, display a MessageBox indicating 
// that DateTimePicker will not accept dates before MinDateTime or 
// after MaxDateTime. Use a StringBuilder object to build the string
// for efficiency.
private void DateTimePicker1_DropDown(object sender, 
    System.EventArgs e)
{

    System.Text.StringBuilder messageBuilder = 
        new System.Text.StringBuilder();
    messageBuilder.Append("Choose a date after: ");
    messageBuilder.Append
        (DateTimePicker.MinDateTime.ToShortDateString());
    messageBuilder.Append(" and a date before: ");
    messageBuilder.Append
        (DateTimePicker.MaxDateTime.ToShortDateString());
    MessageBox.Show(messageBuilder.ToString());
}

' When the calendar drops down, display a MessageBox indicating 
' that DateTimePicker will not accept dates before MinDateTime or 
' after MaxDateTime. Use a StringBuilder object to build the string
' for efficiency.
Private Sub DateTimePicker1_DropDown(ByVal sender As Object, _
    ByVal e As EventArgs) Handles DateTimePicker1.DropDown

    Dim messageBuilder As New System.Text.StringBuilder
    messageBuilder.Append("Choose a date after: ")
    messageBuilder.Append(DateTimePicker.MinDateTime.ToShortDateString)
    messageBuilder.Append(" and a date before: ")
    messageBuilder.Append(DateTimePicker.MaxDateTime.ToShortDateString)
    MessageBox.Show(messageBuilder.ToString())
End Sub

注解

有关处理事件的详细信息，请参阅 处理和引发事件。

另请参阅

• OnDropDown(EventArgs)