VB.NET - 使用Textbox和Combo Box搜索功能

Question

大家好！我想在这里寻求有关我的代码的帮助。主要关注的是从MySQL数据库中搜索文本框提供的关键字。这是我的GUI供参考。

当我在文本框中键入搜索键并在组合框中选择了一列时，搜索查询将在listview上显示其输出。我已尝试过多种组合来获得输出，但无济于事。

这是我帮你的代码。

Private Sub Search()

    lviClientList.Items.Clear()
    Dim strSqlSearch As String = "SELECT code, Company, StAdd, City, ContactPerson, Phone, Mobile, Email, Remarks FROM tblclients WHERE '@Column' LIKE '%" & txtSearchCriteria.Text & "%'"

    Dim item As New ListViewItem()

    If cboColumns.SelectedIndex = 0 Then
        column = "code"
    ElseIf cboColumns.SelectedIndex = 1 Then
        column = "Company"
    ElseIf cboColumns.SelectedIndex = 2 Then
        column = "StAdd"
    ElseIf cboColumns.SelectedIndex = 3 Then
        column = "City"
    ElseIf cboColumns.SelectedIndex = 4 Then
        column = "ContactPerson"
    ElseIf cboColumns.SelectedIndex = 5 Then
        column = "Phone"
    ElseIf cboColumns.SelectedIndex = 6 Then
        column = "Mobile"
    ElseIf cboColumns.SelectedIndex = 7 Then
        column = "Email"
    ElseIf cboColumns.SelectedIndex = 8 Then
        column = "Remarks"
    End If

    Dim mysqlCommand As New MySqlCommand(strSqlSearch, mysqlConnection)
    mysqlCommand.Parameters.AddWithValue("@Column", column)

    Try
        mysqlConnection.Open()
        mysqlReader = mysqlCommand.ExecuteReader()

        Do While mysqlReader.Read()

            item = lviClientList.Items.Add(mysqlReader("code").ToString)
            item.SubItems.Add(mysqlReader("Company").ToString)
            item.SubItems.Add(mysqlReader("StAdd").ToString)
            item.SubItems.Add(mysqlReader("City").ToString)
            item.SubItems.Add(mysqlReader("ContactPerson").ToString)
            item.SubItems.Add(mysqlReader("Phone").ToString)
            item.SubItems.Add(mysqlReader("Mobile").ToString)
            item.SubItems.Add(mysqlReader("Email").ToString)
            item.SubItems.Add(mysqlReader("Remarks").ToString)

        Loop

    Catch ex As Exception

        MsgBox("No results found.", MsgBoxStyle.OkOnly, "Project Analysis System")

    Finally

        mysqlReader.Close()
        mysqlConnection.Close()

    End Try

End Sub

Answer 1

目前尚不清楚为什么您的代码效果不佳。尝试更改Catch子句

中的代码

MsgBox("No results found.", MsgBoxStyle.OkOnly, "Project Analysis System")

到

Msgbox(ex.Message.ToString(), MsgBoxStyle.OkOnly, "Project Analysis System")

所以你会知道确切的错误是什么。

您可以连接ColumnName的值，因为它是在代码中静态设置的。但WHERE上的值应该参数化，因为它是用户输入的值。

尝试修改此代码，

Private Sub Search()

    lviClientList.Items.Clear()
    Dim item As New ListViewItem()
    Dim _isFound As Boolean = False

    Dim colName() As String = {"code", "Company", "StAdd", "City", "ContactPerson", "Phone", "Mobile", "Email", "Remarks"}

    Dim strSqlSearch As String = "SELECT code, Company, StAdd, City, " & _
                                    "ContactPerson, Phone, Mobile, Email, Remarks " & _
                                    "FROM tblclients " & _
                                    "WHERE " & colName(cboColumns.SelectedIndex) & " LIKE CONCAT('%', @valueName, '%')"

    Using myConn As New MySqlConnection("connectionStringHere")
        Using myComm As New MySqlCommand()
            With myComm
                .Connection = myConn
                .CommandType = CommandType.Text
                .CommandText = strSqlSearch
                .Parameters.AddWithValue("@valueName", txtSearchCriteria.Text);
            End With
            Try
                myConn.Open()
                Dim myReader As MySqlDataReader = myComm.ExecuteReader()

                While myReader.Read()
                    _isFound = True
                    item = lviClientList.Items.Add(myReader("code").ToString)
                    item.SubItems.Add(myReader("Company").ToString)
                    item.SubItems.Add(myReader("StAdd").ToString)
                    item.SubItems.Add(myReader("City").ToString)
                    item.SubItems.Add(myReader("ContactPerson").ToString)
                    item.SubItems.Add(myReader("Phone").ToString)
                    item.SubItems.Add(myReader("Mobile").ToString)
                    item.SubItems.Add(myReader("Email").ToString)
                    item.SubItems.Add(myReader("Remarks").ToString)
                End While

                If Not _isFound Then
                    MsgBox("No results found.", MsgBoxStyle.OkOnly, "Project Analysis System")
                End If

            Catch ex As MySqlException
                Msgbox(ex.Message.ToString(), MsgBoxStyle.OkOnly, "Project Analysis System")
            End Try
        End Using
    End Using

End Sub