mysql - 如何过滤 3 个相关的 datagridview

Question

我有 4 个 DataGridView，显示主部门和 3 个子部门:主部门、子部门 1、子部门 2 和子部门 3。
我想单击 Main Department，并希望所有其他 DataGrid 根据直接位于其上方的 DataGrid 中的列重新过滤。
例如
SubDepartment1 将显示与 MainDepartment 相关的记录
SubDepartment2 将显示与 SubDepartment1 相关的记录
SubDepartment3 将显示与 SubDepartment2 相关的记录

我已经有点工作了。我编写了一些方法来填充每个 DataGrid，然后在单击 MainDepartment DataGrid 中的记录时调用所有这些方法。

这会加载主要部门

Private Sub loadmaindept()

    'Dim connstr As String = "database=fabjobs;data source=localhost;userid=root;password=1234"
    Dim connstr As String = ("server='" & My.Settings.setserver & "';
                                   userid='" & My.Settings.setusername & "';
                                   password='" & My.Settings.setpassword & "';
                                   database='" & My.Settings.setdatabase & "'")
    Dim conn As New MySqlConnection(connstr)
    Dim query As String = "select * from maindepartment"

    Try
        conn.Open()
        Dim da As New MySqlDataAdapter(query, conn)
        Dim ds As New DataSet
        da.Fill(ds)
        dgmaindept.DataSource = ds.Tables(0)
        dgmaindept.Refresh()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Close()
        conn.Dispose()
    End Try
End Sub

这会加载与主部门相关的子部门 1

Private Sub loadsub1dept()

    'Dim connstr As String = "database=fabjobs;data source=localhost;userid=root;password=1234"
    Dim connstr As String = ("server='" & My.Settings.setserver & "';
                                   userid='" & My.Settings.setusername & "';
                                   password='" & My.Settings.setpassword & "';
                                   database='" & My.Settings.setdatabase & "'")
    Dim conn As New MySqlConnection(connstr)
    Dim query As String = "select * from sub1department where MainDptid = '" & dgmaindept.CurrentRow.Cells(0).Value.ToString & "'"

    Try
        conn.Open()
        Dim da As New MySqlDataAdapter(query, conn)
        Dim ds As New DataSet
        da.Fill(ds)
        dgsub1dept.DataSource = ds.Tables(0)
        dgsub1dept.Refresh()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Close()
        conn.Dispose()
    End Try
End Sub

这会加载与子部门 1 相关的子部门 2

Private Sub loadsub2dept()

    'Dim connstr As String = "database=fabjobs;data source=localhost;userid=root;password=1234"
    Dim connstr As String = ("server='" & My.Settings.setserver & "';
                                   userid='" & My.Settings.setusername & "';
                                   password='" & My.Settings.setpassword & "';
                                   database='" & My.Settings.setdatabase & "'")
    Dim conn As New MySqlConnection(connstr)
    Dim query As String = "select * from sub2department where Sub1Dptid = '" & dgsub1dept.CurrentRow.Cells(0).Value.ToString & "'"

    Try
        conn.Open()
        Dim da As New MySqlDataAdapter(query, conn)
        Dim ds As New DataSet
        da.Fill(ds)
        dgsub2dept.DataSource = ds.Tables(0)
        dgsub2dept.Refresh()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Close()
        conn.Dispose()
    End Try
End Sub

这会加载与子部门2相关的子部门3

Private Sub loadsub3dept()

    'Dim connstr As String = "database=fabjobs;data source=localhost;userid=root;password=1234"
    Dim connstr As String = ("server='" & My.Settings.setserver & "';
                                   userid='" & My.Settings.setusername & "';
                                   password='" & My.Settings.setpassword & "';
                                   database='" & My.Settings.setdatabase & "'")

    Dim conn As New MySqlConnection(connstr)
        Dim query As String = "select * from sub3department where Sub2Dptid = '" & dgsub2dept.CurrentRow.Cells(0).Value.ToString & "'"

    Try
        conn.Open()
        Dim da As New MySqlDataAdapter(query, conn)
        Dim ds As New DataSet
        da.Fill(ds)
        dgsub3dept.DataSource = ds.Tables(0)
        dgsub3dept.Refresh()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Close()
        conn.Dispose()
    End Try
End Sub

此代码调用子部门的所有其他方法

Private Sub dgmaindept_CellClick(sender As Object, e As DataGridViewCellEventArgs) Handles dgmaindept.CellClick

    Try
        Dim index As Integer
        index = e.RowIndex
        Dim selectedrow As DataGridViewRow
        selectedrow = dgmaindept.Rows(index)

        lblmainid.Text = selectedrow.Cells(0).Value.ToString()
        txtmaindeptno.Text = selectedrow.Cells(1).Value.ToString()
        txtmaindescription.Text = selectedrow.Cells(2).Value.ToString()
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try

    loadsub1dept()
    loadsub2dept()
    loadsub3dept()

End Sub

我希望当我单击主要部门中的任何记录时，网格都会自动过滤。只要我在子部门 1 中有记录，它就可以工作，但是当我单击没有子部门 1 记录的主部门记录时，我会在子部门 2 方法中收到 Null reference unhandled 错误。

Answer 1

将您的 loadXdept() sub 也放入 try/catch 处理程序中