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vb.net - 来自不同形式的错误会赶上其他形式

问题描述

如果您能帮助我解决 vb.net 项目中的奇怪行为，我将不胜感激。

我有一个登录表单。用户提供用户名和密码，如果凭据正常，应用程序会转到另一个表单

Try
        con.Open()
        Dim sql As New SQLite.SQLiteCommand("Select * From users where username = '" & UsernameTextBox.Text & "' and userpass = '" & PasswordTextBox.Text & "'", con)
        Dim dr As SQLite.SQLiteDataReader = sql.ExecuteReader
        Dim dt As New DataTable
        dt.Load(dr)
        If dt.Rows.Count = 1 Then
            'there is only one user
            Dim f As New MainFrm
            f.lbluser.Tag = dt.Rows(0)(3)
            f.lbluser.Text = dt.Rows(0)(1)
            f.ShowDialog()
            Me.Close()
        ElseIf dt.Rows.Count = 0 Then
            'credentials are wrong
            MessageBox.Show("No user with those credentials. Try again!", "Wrong credentials", MessageBoxButtons.OK, MessageBoxIcon.Error)
            UsernameTextBox.Text = ""
            PasswordTextBox.Text = ""
            UsernameTextBox.Focus()
            Exit Sub
        Else
            'credentials are multiple in the database
            MessageBox.Show("Issues with the credentials. Code error: LFUE-1010", "Multiple users | LFUE-1010", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Exit Sub
        End If
        con.Close()
    Catch ex As Exception
        con.Close()
        'there are problems with the connection / or sql
        MessageBox.Show("Connection issues - code error: LFDC-1020 " & ex.Message, "DB connection error | LFDC-1020", MessageBoxButtons.OK, MessageBoxIcon.Error)
    End Try

这完美地工作。在另一种形式中，假设我有一个按钮：

If cbkeywords.SelectedIndex = -1 Then
        MsgBox("select something")
        Exit Sub
    End If
    Dim d = DirectCast(cbkeywords.SelectedItem, DataRowView).Item("Keyword")
    If lstkeywords.Items.Count > 0 Then
        For i As Integer = 0 To lstkeywords.Items.Count - 1
            If lstkeywords.Items(i).contains(d) Then
                MessageBox.Show("there is already value " & d, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                Exit Sub
            Else
                dtkeys.Rows.Add(cbkeywords.SelectedValue, d)
                lstkeywords.Items.Add(d)
            End If
        Next
    Else
        dtkeys.Rows.Add(cbkeywords.SelectedValue, d)
        lstkeywords.Items.Add(d)
    End If

如果代码有错误，则应用程序转到登录表单 Catch ex As Exception 并获取消息。

每当我遇到不同形式的代码问题时，应用程序都会转到 Login Form Catch ex As Exception。

我清理了解决方案、项目、重新启动，但没有任何改变。有任何想法吗？提前致谢

标签： vb.netformstry-catch

解决方案

先做数据库代码，然后再做其他代码。将它们分开。否则，当你这样做时f.ShowDialog()，它仍然在 Try...Catch 中。

像这样的东西：

Dim dt As New DataTable

Dim con As New SqliteConnection(yourConnectionString)

Try
    Dim sql As New SQLite.SQLiteCommand("Select * From users where username = '" & UsernameTextBox.Text & "' and userpass = '" & PasswordTextBox.Text & "'", con)
    Dim dr As SQLite.SQLiteDataReader = sql.ExecuteReader()
    dt.Load(dr)

Catch ex As Exception
    con.Close()
    'there are problems with the connection / or sql
    MessageBox.Show("Connection issues - code error: LFDC-1020 " & ex.Message, "DB connection error | LFDC-1020", MessageBoxButtons.OK, MessageBoxIcon.Error)

Finally
    If Sql IsNot Nothing Then
        Sql.Dispose()
    End If

    If con IsNot Nothing Then
        con.Dispose()
    End If

End Try

If dt.Rows.Count = 1 Then
    'there is only one user
    Dim f As New MainFrm
    f.lbluser.Tag = dt.Rows(0)(3)
    f.lbluser.Text = dt.Rows(0)(1)
    f.ShowDialog()
    Me.Close()
ElseIf dt.Rows.Count = 0 Then
    'credentials are wrong
    MessageBox.Show("No user with those credentials. Try again!", "Wrong credentials", MessageBoxButtons.OK, MessageBoxIcon.Error)
    UsernameTextBox.Text = ""
    PasswordTextBox.Text = ""
    UsernameTextBox.Focus()
    Exit Sub
Else
    'credentials are multiple in the database
    MessageBox.Show("Issues with the credentials. Code error: LFUE-1010", "Multiple users | LFUE-1010", MessageBoxButtons.OK, MessageBoxIcon.Error)
    Exit Sub
End If

您不需要打开连接，因为该.Load方法会执行此操作，然后将连接保持在原来的状态。

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