Visual Basic輸入框關閉錯誤

Question

這是一個奇怪的問題，並且對這個問題包含的大量代碼表示歉意，但是，我已經給了其他人的項目來維護，並且用戶已經找到了我一個錯誤。有一個按鈕可以打開InputBox，如下所示。

的形式用於輸入文件的路徑導入。如果用戶沒有輸入路徑或不正確的路徑，則顯示錯誤 - 很好。現在，問題是，如果用戶按下「取消」按鈕或右上角的x關閉表單，它也會返回相同的錯誤，表示無法找到路徑。

通過以下代碼查看後，我無法弄清楚如何使它在按下x或Cancel時不顯示錯誤，那麼任何人都可以幫我解決問題嗎？

Private Sub btnImport_Click(sender As Object, e As EventArgs) Handles btnImport.Click 

    Try 
     Dim importbox As String = InputBox("Input path", "Import", "") 
     Dim fi As New FileInfo(importbox) 
     Dim connectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Extended Properties=Text;Data Source=" & fi.DirectoryName 

     Dim conn As New OleDbConnection(connectionString) 
     conn.Open() 

     Dim add1 As String = "" 
     Dim add2 As String = "" 
     Dim add3 As String = "" 
     Dim add4 As String = "" 
     Dim add5 As String = "" 
     Dim postcode As String = "" 
     Dim telephone As String = "" 
     Dim fax As String = "" 
     Dim email As String = "" 
     Dim customercode As String = "" 
     Dim customername As String = "" 
     Dim webpage As String = "" 
     Dim mobile As String = "" 

     Dim headerTable As DataTable = ugHeaders.DataSource 
     Dim csvArray(headerTable.Rows.Count) As String 
     Dim i As Integer = 0 
     For Each dr As DataRow In headerTable.Rows 
      csvArray(i) = dr.Item("CSVName") 
     Next 

     For Each dr As DataRow In headerTable.Rows 
      Select Case dr.Item("DBName").ToString.Trim 
       Case "Add1" 
        add1 = dr.Item("CSVName") 
       Case "Add2" 
        add2 = dr.Item("CSVName") 
       Case "Add3" 
        add3 = dr.Item("CSVName") 
       Case "Add4" 
        add4 = dr.Item("CSVName") 
       Case "Add5" 
        add5 = dr.Item("CSVName") 
       Case "PostCode" 
        postcode = dr.Item("CSVName") 
       Case "Telephone" 
        telephone = dr.Item("CSVName") 
       Case "Fax" 
        fax = dr.Item("CSVName") 
       Case "Email" 
        email = dr.Item("CSVName") 
       Case "Customer_Name" 
        customername = dr.Item("CSVName") 
       Case "Customer_Code" 
        customercode = dr.Item("CSVName") 
       Case "webpage" 
        webpage = dr.Item("CSVName") 
       Case "mobile_phone" 
        mobile = dr.Item("CSVName") 
      End Select 
     Next 

     Dim sqlSelect As String = "SELECT Company, [" & add1 & "], [" & add3 & "], [" & postcode & "], [" & add2 & "], " & _ 
              "[" & telephone & "], [" & fax & "], [" & email & "], [" & customercode & "], " & _ 
              "[" & add4 & "], [" & add5 & "], [" & webpage & "], [" & mobile & "] FROM " & fi.Name 

     Dim cmdSelect As New OleDbCommand(sqlSelect, conn) 

     Dim adapter1 As New OleDbDataAdapter(cmdSelect) 

     Dim ds As New DataSet 
     adapter1.Fill(ds, "DATA") 

     pb_progress.Maximum = ds.Tables(0).Rows.Count 
     pb_progress.Value = 0 

     For Each dr As DataRow In ds.Tables(0).Rows 
      Try 
       Debug.WriteLine(dr.Item(customercode).ToString.Trim) 

       If dr.Item(customercode).ToString.Trim = "" Then 
        Dim str As String = dr.Item(customername) 
        If str.Trim = "" Then Continue For 
        Dim length As Integer = str.Length 
        If length < 20 Then 
        Else 
         length = 20 
        End If 

        str = Replace(str.Substring(0, length), " ", "_").ToUpper 
        str = Regex.Replace(str, "[^a-zA-Z _&]", "") 

        Dim found As Boolean = True 
        Dim loopcount As Integer = 1 

        Do Until found = False 
         Dim checkSql As String = "SELECT * FROM Customers WHERE [Customer_Code] = @ccode" 
         Dim checkCmd As New OleDb.OleDbCommand(checkSql, con) 
         checkCmd.Parameters.AddWithValue("@ccode", str) 
         Dim checkDa As New OleDb.OleDbDataAdapter(checkCmd) 
         Dim checkDt As New DataTable 
         checkDa.Fill(checkDt) 

         If checkDt.Rows.Count <> 0 Then 
          found = True 
          str &= CStr(loopcount) 
          loopcount += 1 
         Else 
          found = False 
         End If 
        Loop 

        dr.Item(customercode) = str 
       Else 
        Dim found As Boolean = True 
        Dim loopcount As Integer = 1 
        Do Until found = False 
         Dim checkSql As String = "SELECT * FROM Customers WHERE [Customer_Code] = @ccode" 
         Dim checkCmd As New OleDb.OleDbCommand(checkSql, con) 
         checkCmd.Parameters.AddWithValue("@ccode", dr.Item(customercode)) 
         Dim checkDa As New OleDb.OleDbDataAdapter(checkCmd) 
         Dim checkDt As New DataTable 
         checkDa.Fill(checkDt) 

         If checkDt.Rows.Count <> 0 Then 
          found = True 
          dr.Item(customercode) &= CStr(loopcount) 
          loopcount += 1 
         Else 
          found = False 
         End If 
        Loop 
       End If 

       Dim sql As String 
       sql = "INSERT INTO Customers(Customer_Code, Customer_Name, Contract_Payment_Terms, Aq_Date, Telephone, Fax, Email, Average_Payment_Terms, webpage, mobile_phone) " & _ 
        "VALUES(@ccode, @cname, 30, #01/01/2016#, @ctele, @cfax, @email, 30, @webpage, @mobile);" 
       Dim cmd As New OleDb.OleDbCommand(sql, con) 
       With cmd.Parameters 
        .AddWithValue("@ccode", dr.Item(customercode)) 
        .AddWithValue("@cname", dr.Item(customername)) 
        .AddWithValue("@ctele", dr.Item(telephone).ToString.Truncate(48)) 
        .AddWithValue("@cfax", dr.Item(fax)) 
        .AddWithValue("@email", dr.Item(email)) 
        .AddWithValue("@webpage", dr.Item(webpage)) 
        .AddWithValue("@mobile", dr.Item(mobile)) 
       End With 
       cmd.ExecuteNonQuery() 

       sql = "INSERT INTO [Customer_Addresses] (Cust_Code, PostCode, Alias, Add1, Add2, Add3, Add4, Add5) VALUES(@ccode, @pcode, 'Default'" & _ 
        ",@add1, @add2, @add3, @add4, @add5);" 
       cmd = New OleDb.OleDbCommand(sql, con) 
       With cmd.Parameters 
        .AddWithValue("@ccode", dr.Item(customercode)) 
        .AddWithValue("@pcdoe", dr.Item(postcode)) 
        .AddWithValue("@add1", dr.Item(add1)) 
        .AddWithValue("@add2", dr.Item(add2)) 
        .AddWithValue("@add3", dr.Item(add3)) 
        .AddWithValue("@add4", dr.Item(add4)) 
        .AddWithValue("@add5", dr.Item(add5)) 
       End With 
       cmd.ExecuteNonQuery() 

      Catch ex As Exception 
       Debug.WriteLine(ex.Message) 
      End Try 


      pb_progress.Increment(1) 
     Next 

     MsgBox("Import successful", MsgBoxStyle.OkOnly, "Success") 

    Catch ex As Exception 
     errorLog(ex) 
    End Try 
End Sub 

Answer 1

Inputbox將始終return一個String。

• 如果用戶按下「確定」，它將返回String放入TextBox。
• 如果他通過按X或取消它取消框returns ""。

我通常不會建議使用Inputbox來獲取文件路徑。改爲使用OpenFileDialog。如果您的Clipboard中已有完整路徑，則只需將其粘貼到OFD的Filename-Textbox中，然後按回車。

這應該讓你開始：

Dim ofd as new OpenFileDialog() 
// Show the File Dialog to the user and detect he pressed OK or Cancelled 
if ofd.ShowDialog = Windows.Forms.DialogResult.OK 
     // Always check, if the file really exists 
     if IO.File.exists(ofd.FileName) 
     importbox = ofd.FileName 
     Else 
     msgbox("File does not exist") 
     Exit Sub 
     End if 
Else 
    Exit Sub 
End if