RunWorkerCompletedEventArgs 类

定义

命名空间:

System.ComponentModel

程序集:

System.ComponentModel.EventBasedAsync.dll

Source:

RunWorkerCompletedEvent.cs

为 MethodNameCompleted 事件提供数据。

public ref class RunWorkerCompletedEventArgs : System::ComponentModel::AsyncCompletedEventArgs

public class RunWorkerCompletedEventArgs : System.ComponentModel.AsyncCompletedEventArgs

type RunWorkerCompletedEventArgs = class
    inherit AsyncCompletedEventArgs

Public Class RunWorkerCompletedEventArgs
Inherits AsyncCompletedEventArgs

继承

Object

EventArgs

AsyncCompletedEventArgs

RunWorkerCompletedEventArgs

示例

以下代码示例阐释了 RunWorkerCompletedEventArgs 的用法。 此示例是 类的较大示例的 BackgroundWorker 一部分。

// This event handler deals with the results of the
// background operation.
void backgroundWorker1_RunWorkerCompleted( Object^ /*sender*/, RunWorkerCompletedEventArgs^ e )
{
   // First, handle the case where an exception was thrown.
   if ( e->Error != nullptr )
   {
      MessageBox::Show( e->Error->Message );
   }
   else
   if ( e->Cancelled )
   {
      // Next, handle the case where the user cancelled 
      // the operation.
      // Note that due to a race condition in 
      // the DoWork event handler, the Cancelled
      // flag may not have been set, even though
      // CancelAsync was called.
      resultLabel->Text = "Cancelled";
   }
   else
   {
      // Finally, handle the case where the operation 
      // succeeded.
      resultLabel->Text = e->Result->ToString();
   }

   // Enable the UpDown control.
   this->numericUpDown1->Enabled = true;

   // Enable the Start button.
   startAsyncButton->Enabled = true;

   // Disable the Cancel button.
   cancelAsyncButton->Enabled = false;
}

// This event handler deals with the results of the
// background operation.
private void backgroundWorker1_RunWorkerCompleted(
    object sender, RunWorkerCompletedEventArgs e)
{
    // First, handle the case where an exception was thrown.
    if (e.Error != null)
    {
        MessageBox.Show(e.Error.Message);
    }
    else if (e.Cancelled)
    {
        // Next, handle the case where the user canceled 
        // the operation.
        // Note that due to a race condition in 
        // the DoWork event handler, the Cancelled
        // flag may not have been set, even though
        // CancelAsync was called.
        resultLabel.Text = "Canceled";
    }
    else
    {
        // Finally, handle the case where the operation 
        // succeeded.
        resultLabel.Text = e.Result.ToString();
    }

    // Enable the UpDown control.
    this.numericUpDown1.Enabled = true;

    // Enable the Start button.
    startAsyncButton.Enabled = true;

    // Disable the Cancel button.
    cancelAsyncButton.Enabled = false;
}

' This event handler deals with the results of the
' background operation.
Private Sub backgroundWorker1_RunWorkerCompleted( _
ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) _
Handles backgroundWorker1.RunWorkerCompleted

    ' First, handle the case where an exception was thrown.
    If (e.Error IsNot Nothing) Then
        MessageBox.Show(e.Error.Message)
    ElseIf e.Cancelled Then
        ' Next, handle the case where the user canceled the 
        ' operation.
        ' Note that due to a race condition in 
        ' the DoWork event handler, the Cancelled
        ' flag may not have been set, even though
        ' CancelAsync was called.
        resultLabel.Text = "Canceled"
    Else
        ' Finally, handle the case where the operation succeeded.
        resultLabel.Text = e.Result.ToString()
    End If

    ' Enable the UpDown control.
    Me.numericUpDown1.Enabled = True

    ' Enable the Start button.
    startAsyncButton.Enabled = True

    ' Disable the Cancel button.
    cancelAsyncButton.Enabled = False
End Sub

注解

将基于事件的异步模式用于异步操作时，Windows 窗体窗体或控件通过调用 BackgroundWorker.RunWorkerAsync 方法启动异步操作。 方法反过来异步引发 事件， BackgroundWorker.DoWork 并向其传递实例 DoWorkEventArgs 。 如果异步操作返回值，则 BackgroundWorker.DoWork 事件处理程序通常会将其 DoWorkEventArgs.Result 分配给 属性。 异步操作完成后， BackgroundWorker.RunWorkerCompleted 将引发该事件，并向其传递一个 RunWorkerCompletedEventArgs 实例，该实例包含有关操作状态的信息 (该操作是否已取消、出错或成功完成) 。 如果成功完成，则其 Result 属性包含异步操作返回的值，并且之前分配给该 DoWorkEventArgs.Result 属性。

注意

HostProtectionAttribute应用于此类的属性具有以下Resources属性值：SharedState。 HostProtectionAttribute 不影响桌面应用程序（通常通过双击图标、键入命令或在浏览器中输入 URL 来启动这些应用程序）。 有关详细信息，请参阅 HostProtectionAttribute 类或SQL Server编程和主机保护属性。

构造函数

RunWorkerCompletedEventArgs(Object, Exception, Boolean)

初始化 RunWorkerCompletedEventArgs 类的新实例。

属性

Cancelled	获取一个值，该值指示异步操作是否已被取消。 (继承自 AsyncCompletedEventArgs)
Error	获取一个值，该值指示异步操作期间发生的错误。 (继承自 AsyncCompletedEventArgs)
Result	获取表示异步操作结果的值。
UserState	获取表示用户状态的值。

方法

Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
RaiseExceptionIfNecessary()	如果异步操作失败，则引发用户提供的异常。 (继承自 AsyncCompletedEventArgs)
ToString()	返回表示当前对象的字符串。 (继承自 Object)

另请参阅

• BackgroundWorker
• 如何：在后台运行操作
• 如何：在后台下载文件