VB.NET - 使用文本框和组合框的搜索功能

Question

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

当我键入文本框，并在组合框中选择一个栏我的搜索关键字，搜索查询将其在列表视图输出。我试过很多组合来获得输出，但无济于事。

这是我的代码，可以帮助我。

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

不清楚为什么你的代码不能正常工作。尝试改变的代码在你的Catch条款

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

到

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

所以你就会知道确切的错误是什么。

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

试试这个修改代码，

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