表单和错误消息中的任务功能

Question

我有一个表单，它的作用是在用户等待完成特定任务时向用户显示循环进度图形。这是它的简单代码：

Public Class FrmCircularProgress
    Sub New(progressType As DevComponents.DotNetBar.eCircularProgressType)
        InitializeComponent()
        CircularProgress1.ProgressBarType = progressType
        StartCircular()
    End Sub

    Public Sub StartCircular()
        Me.CircularProgress1.IsRunning = True
    End Sub

    Public Sub StopCircular()
        Me.CircularProgress1.IsRunning = False
    End Sub
End Class

以下是我如何使用它的示例（在本例中为两个地方）

 Dim createArticle As New Artikel

                    'http://stackoverflow.com/questions/33030706/put-long-running-method-into-task-showing-new-form-meantime-and-closing-it-once
                    Dim pic As New FrmCircularProgress(eCircularProgressType.Donut)
                    Dim tsk As Task(Of Boolean) = Task.Factory.StartNew(Of Boolean)(Function()
                                                                                        '--Run lenghty task
                                                                                        Dim resu = False
                                                                                        Try
                                                                                            resu = createArticle.ProcessArticle(_artikelsAndTheirVariationsFinal)
                                                                                            '--Close form once done (on GUI thread)

                                                                                        Catch sqlex As Exception
                                                                                            pic.Invoke(Sub() MessageBox.Show(pic, sqlex.Message))
                                                                                            ' pic.Invoke(Sub() MessageBox.Show(pic, ex.Message))
                                                                                            'pic.Invoke(Sub() TaskDialog.Show(pic, New TaskDialogInfo("Information", eTaskDialogIcon.BlueStop, "WizardPageDescriptionUberblick_BeforePageDisplayed", ex.ToString, eTaskDialogButton.Ok, eTaskDialogBackgroundColor.Blue, Nothing, Nothing, Nothing, "Jakis footer text", Nothing)))
                                                                                        Finally

                                                                                        End Try

                                                                                        pic.Invoke(New Action(Sub() pic.StopCircular()))
                                                                                        pic.Invoke(New Action(Sub() pic.Close()))
                                                                                        Return resu
                                                                                    End Function)

                    '--Show the form
                    pic.ShowDialog()
                    Task.WaitAll(tsk)

                    If tsk.Result = True Then
                        TaskDialog.Show(New TaskDialogInfo("Information", eTaskDialogIcon.BlueStop, "Infor", "New articel and every data has been added correctly", eTaskDialogButton.Ok, eTaskDialogBackgroundColor.Blue, Nothing, Nothing, Nothing, "Jakis footer text", Nothing))

                        'http://stackoverflow.com/questions/33030706/put-long-running-method-into-task-showing-new-form-meantime-and-closing-it-once
                        pic = New FrmCircularProgress(eCircularProgressType.Line)
                        Dim work As Task = Task.Factory.StartNew(Sub()
                                                                     '--Run lenghty task
                                                                     PrepareUberblick()
                                                                     '--Close form once done (on GUI thread)
                                                                     pic.Invoke(New Action(Sub() pic.StopCircular()))
                                                                     pic.Invoke(New Action(Sub() pic.Close()))
                                                                 End Sub)

                        '--Show the form
                        pic.ShowDialog()
                        Task.WaitAll(work)

                        If WYSWIG_Uberblick.Document IsNot Nothing Then
                            WYSWIG_Uberblick.Document.Write(String.Empty)
                        End If

                        '--Pobranie wszystkich html'ow wszystkich podsekcji artykulow (w tym wypadku numerów artykułów jako podsekcji) (dla sekcji Uberblick)
                        WYSWIG_Uberblick.DocumentText = _htmlFactory.GetAllUberblickHTML
                    Else
                        TaskDialog.Show(New TaskDialogInfo("Information", eTaskDialogIcon.NoEntry, "Infor", "Critical error occured", eTaskDialogButton.Ok, eTaskDialogBackgroundColor.Blue, Nothing, Nothing, Nothing, "Jakis footer text", Nothing))
                        e.Cancel = True
                    End If

ProcessArticle 函数：

Public Function ProcessArticle(artikel As ArticlesVariations) As Boolean

        Dim result = True
        Dim strcon = New AppSettingsReader().GetValue("ConnectionString", GetType(System.String)).ToString()

        Using connection As New SqlConnection(strcon)
            '-- Open generall connection for all the queries
            connection.Open()
            '-- Make the transaction.
            Dim transaction As SqlTransaction
            transaction = connection.BeginTransaction(IsolationLevel.ReadCommitted)

            Dim newArticleRowId As Integer = 0
            Dim articleIndex As Integer = 0
            Try
                For Each kvp As KeyValuePair(Of Integer, Artikel) In artikel.collection
                    Dim ckey As Integer = kvp.Key
                    articleIndex = kvp.Key              'save article key
                    Dim data As Artikel = kvp.Value

                    '-- If given article contains images list (artikel_images is a list with pictures associated with article)
                    If Not IsNothing(artikel.collection(articleIndex).ArtikelImages) Then
                        For Each img In artikel.collection(articleIndex).ArtikelImages
                            '--Insert article's images if exists
                            Using cmd As New SqlCommand("INSERT INTO T_Article_Image (Path, FK_Artikel_ID, Position) VALUES (@Path, @FK_Artikel_ID, @Position)", connection)
                                cmd.CommandType = CommandType.Text
                                cmd.Connection = connection
                                cmd.Transaction = transaction
                                cmd.Parameters.AddWithValue("@Path", img.Path)
                                cmd.Parameters.AddWithValue("@FK_Artikel_ID", newArticleRowId)
                                cmd.Parameters.AddWithValue("@Position", img.Position)
                                cmd.ExecuteScalar()
                            End Using
                        Next
                    End If

                    '-- If given article contains articles variations list (artikel_variation_attributes is a list with variations associated with article)
                    If Not IsNothing(artikel.collection(articleIndex)._artikel_variation_attributes) Then
                        For Each var In artikel.collection(articleIndex)._artikel_variation_attributes

                            '--Insert article's images if exists
                            Using cmd As New SqlCommand("INSERT INTO T_Artikel_T_Variation (FK_Variation_VariationAttribute_ID, FK_Artikel_ID, Position) VALUES (@FK_Variation_VariationAttribute_ID, @FK_Artikel_ID, @Position)", connection)
                                cmd.CommandType = CommandType.Text
                                cmd.Connection = connection
                                cmd.Transaction = transaction
                                cmd.Parameters.AddWithValue("@FK_Variation_VariationAttribute_ID", New Variation_VariationAttribute(var.FkVariationId, var.FkVariationAttributeId).GetId())
                                cmd.Parameters.AddWithValue("@FK_Artikel_ID", newArticleRowId)
                                cmd.Parameters.AddWithValue("@Position", var.Position)
                                cmd.ExecuteScalar()
                            End Using
                        Next
                    End If

                Next
                transaction.Commit()
            Catch ex As Exception
                result = False
                '-- Roll the transaction back.
                Try
                    transaction.Rollback()
                Catch ex2 As Exception
                    ' This catch block will handle any errors that may have occurred
                    ' on the server that would cause the rollback to fail, such as
                    ' a closed connection.
                    'Console.WriteLine("Rollback Exception Type: {0}", ex2.GetType())
                    'Console.WriteLine("  Message: {0}", ex2.Message)
                End Try

            End Try
        End Using

        Return result
    End Function

然而，当涉及到错误或这些方法中的任何问题时，一切正常（来自我们的示例）：

Dim resu As Boolean = createArticle.ProcessArticle(_artikelsAndTheirVariationsFinal)

或者这个方法：

PrepareUberblick()

我的循环表单没有关闭，但它仍在运行（卡住了）。当我使用Alt+F4 杀死我的圆形表单时，我看到一条错误消息。我假设发生错误时，错误消息窗口不会显示在前面，而是隐藏在圆形表单后面。

这里的问题是：你知道如何解决它，所以当发生错误时，错误消息会显示在前面，以便用户可以确认然后关闭循环表单？

Answer 1

如果你想提醒用户发生了什么事，你可以从你的圆形表单中显示 MessageBox，它应该出现在它的顶部，因为它是在同一个线程上生成的。您可以在Catch中显示MessageBox

Try
    '--Run lenghty task
    resu = createArticle.ProcessArticle(_artikelsAndTheirVariationsFinal)
Catch ex As Exception
    pic.Invoke(Sub() MessageBox.Show(ex.message))
End Try
'--Close form once done (on GUI thread)        
pic.Invoke(New Action(Sub() pic.StopCircular()))
pic.Invoke(New Action(Sub() pic.Close()))

这样，用户需要在循环表单关闭之前点击 MessageBox 上的“确定”。

您的整个问题源于您没有在创建表单的同一线程上调用 MessageBox.Show() 。从您的示例中不清楚表单的创建位置，无论它是否在 UI 线程上。在任何一种情况下，创建表单的任何线程都必须与引发消息框的线程相同，以便 MessageBox 成为表单的模态。通过调用pic.Invoke(Sub() MessageBox.Show(ex.message))，您可以确保它显示在表单的线程上，并且是模态的。您通常可以使用 overload 强制父窗口具有

Public Shared Function Show (
    owner As IWin32Window,
    text As String
) As DialogResult

应该是

pic.Invoke(Sub() MessageBox.Show(pic, ex.message))

另见：

Does MessageBox.Show() automatically marshall to the UI Thread?

Why use a owner window in MessageBox.Show?