VB.NET SQL 数据库锁定

Question

我的数据表在 2 个地方加载，一个 DataGridView 和一个 ComboBox ComboBox是选择要编辑的记录（一个TextBox输入新值） 而DataGridView是看变化的（我放弃了（暂时）直接从DataGridView更新）

Private Sub EditLoc_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Try
        con.Open()


        Dim sql = Nothing

        sql = "SELECT Location FROM Location"


        Dim cmdDataGrid As SQLiteCommand = New SQLiteCommand(sql, con)


        Dim da As New SQLiteDataAdapter
        da.SelectCommand = cmdDataGrid
        Dim dt As New DataTable
        da.Fill(dt)
        DataGridView1.DataSource = dt

        Dim readerDataGrid As SQLiteDataReader = cmdDataGrid.ExecuteReader()

        con.Close()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try



    Try ' TRY CATCH for combobox

        con.Open()
        cmd.Connection = con
        cmd.CommandText = "SELECT Location FROM Location"


        dr = cmd.ExecuteReader()

        ' Fill a combo box with the datareader
        Do While dr.Read = True
            ComboBox1.Items.Add(dr.GetString(0))
        Loop

        If ComboBox1.Items.Count > 0 Then
            ComboBox1.SelectedIndex = 0 ' The first item has index 0 '
        End If

        con.Close()

    Catch ex As Exception
        MsgBox(ex.Message)

    End Try


End Sub

这很好用 Picture

问题是当我点击保存时，应用程序挂起一段时间，然后我收到“数据库已锁定”错误picture

这是保存按钮的代码：

Private Sub Savebtn_Click(sender As Object, e As EventArgs) Handles Savebtn.Click

    Try
        con.Open()
        cmd = con.CreateCommand
        cmd.CommandText = "UPDATE Location set Location = '" & TextBox1.Text & "' WHERE Location = '" & ComboBox1.Text & "'"
        cmd.ExecuteNonQuery()
        cmd.Dispose()

        con.Close()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

End Sub

感谢您的帮助

Answer 1

我通过从代码中删除所有“cmd.Dispose()”、“da.Dispose()”和“con.Close()”来解决这个问题，只保留它们

Private Sub Closebtn_Click(sender As Object, e As EventArgs) Handles Closebtn.Click
    da.Dispose()
    cmd.Dispose()
    con.Close()
    Dim fems As New EMS
    fems.Show()
    Me.Close()
End Sub

在表单加载时我有

Private Sub EditLoc_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    con.Open()
    Call pull()
End Sub

Pull sub 拥有其余的一切......

Private Sub pull()
    Try
        Dim sql = Nothing
        sql = "SELECT Location FROM Location"
        Dim cmdDataGrid As SQLiteCommand = New SQLiteCommand(sql, con)
        da.SelectCommand = cmdDataGrid
        Dim dt As New DataTable
        da.Fill(dt)
        DataGridView1.DataSource = dt
        Dim readerDataGrid As SQLiteDataReader = cmdDataGrid.ExecuteReader()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

    Try ' TRY CATCH for combobox
        cmd.Connection = con
        cmd.CommandText = "SELECT Location FROM Location"
        dr = cmd.ExecuteReader()
        ' Fill a combo box with the datareader
        Do While dr.Read = True
            ComboBox1.Items.Add(dr.GetString(0))
        Loop
        If ComboBox1.Items.Count > 0 Then
            ComboBox1.SelectedIndex = 0 ' The first item has index 0 '
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

End Sub

这是我的保存按钮

Private Sub Savebtn_Click(sender As Object, e As EventArgs) Handles Savebtn.Click

    If Not TextBox1.Text = Nothing Then
        Try
            cmd = con.CreateCommand
            cmd.CommandText = "UPDATE Location set Location = '" & TextBox1.Text & "' WHERE Location = '" & ComboBox1.Text & "'"
            cmd.ExecuteNonQuery()

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

        Call pull()
        TextBox1.Text = Nothing

    End If

End Sub

现在一切正常，没有错误！

保存后调用 pull() 会更新 DataGridView

感谢您的帮助