Question

我在asp.net＆amp;中制作网页在后端使用mysql ..我的问题是onpage load data显示正常。我对数据应用了一些过滤器，这对我来说不起作用。

ERROR

System.InvalidOperationException：CommandText属性没有已正确初始化。在 MySql.Data.MySqlClient.ExceptionInterceptor.Throw（异常异常）在

VB代码

Protected Sub area_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles area.SelectedIndexChanged
        Try
            ViewState("Data") = ""
            If area.SelectedValue <> "All" And board.SelectedValue <> "All" Then
                query = "SELECT * FROM school"

            ElseIf area.SelectedValue <> "All" And board.SelectedValue <> "All" Then
                query = "SELECT * FROM `school` WHERE area = '" + area.SelectedValue + "';"

            ElseIf area.SelectedValue <> "All" And board.SelectedValue <> "All" Then
                query = "SELECT * FROM 'school' WHERE board = '" + board.SelectedValue + "'; "

            End If
                Using con As New MySqlConnection(constr)
                Using cmd As New MySqlCommand(query, con)
                    Using sda As New MySqlDataAdapter()
                        cmd.Connection = con
                        sda.SelectCommand = cmd
                        cmd.CommandTimeout = 0
                        Using dt As New DataTable()
                            sda.Fill(dt)
                            ViewState("Data") = dt
                            schoollists.DataSource = dt
                            schoollists.DataBind()

                        End Using
                    End Using
                End Using
                End Using

                countResult.Text = (" " & schoollists.Items.Count & " " & board.Text & " Schools Found in " & area.Text & " ")

        Catch ex As Exception
            Response.Write(ex)
        End Try
    End Sub

连接字符串

<add name="constr" connectionString="Data Source=localhost;port=3306;Initial Catalog=vidyan;User Id=root;password="/>

无法过滤listview

0 个答案: