DoWorkEventHandler 委托
重要
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表示用来处理 DoWork 事件的方法。 此类不能被继承。
public delegate void DoWorkEventHandler(System::Object ^ sender, DoWorkEventArgs ^ e);
public delegate void DoWorkEventHandler(object sender, DoWorkEventArgs e);
public delegate void DoWorkEventHandler(object? sender, DoWorkEventArgs e);
type DoWorkEventHandler = delegate of obj * DoWorkEventArgs -> unit
Public Delegate Sub DoWorkEventHandler(sender As Object, e As DoWorkEventArgs)
- sender
- Object
事件源。
包含事件数据的 DoWorkEventArgs。
下面的代码示例演示如何使用 DoWorkEventHandler 委托来处理 DoWork 事件。 有关完整代码列表,请参阅 如何:在后台运行操作。
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// Do not access the form's BackgroundWorker reference directly.
// Instead, use the reference provided by the sender parameter.
BackgroundWorker bw = sender as BackgroundWorker;
// Extract the argument.
int arg = (int)e.Argument;
// Start the time-consuming operation.
e.Result = TimeConsumingOperation(bw, arg);
// If the operation was canceled by the user,
// set the DoWorkEventArgs.Cancel property to true.
if (bw.CancellationPending)
{
e.Cancel = true;
}
}
Private Sub backgroundWorker1_DoWork( _
sender As Object, e As DoWorkEventArgs) _
Handles backgroundWorker1.DoWork
' Do not access the form's BackgroundWorker reference directly.
' Instead, use the reference provided by the sender parameter.
Dim bw As BackgroundWorker = CType( sender, BackgroundWorker )
' Extract the argument.
Dim arg As Integer = Fix(e.Argument)
' Start the time-consuming operation.
e.Result = TimeConsumingOperation(bw, arg)
' If the operation was canceled by the user,
' set the DoWorkEventArgs.Cancel property to true.
If bw.CancellationPending Then
e.Cancel = True
End If
End Sub
创建 DoWorkEventHandler 委托时,需要标识将处理该事件的方法。 若要将事件与事件处理程序关联,请将该委托的一个实例添加到事件中。 除非删除委托,否则每当事件发生时,都调用事件处理程序方法。 有关事件处理程序委托的详细信息,请参阅 处理和引发事件。
Get |
获取指示指定委托表示的方法的对象。 |
产品 | 版本 |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 2.0, 2.1 |
UWP | 10.0 |