使用 Visual Basic 执行 MySQL 查询

Question

我正在尝试连接到 MySQL 服务器，从文本框中获取输入，使用该信息运行查询并将其存储在列表框中。

更进一步，我想在文本框中键入内容时更新列表框。

每当我运行 vb 时，都不会填充任何内容。我什至尝试将查询更改为基本的查询，select * from securePasswordList.users;而且我无法填充任何内容。

有什么建议或批评吗？谢谢!仍在学习很多关于 VB 的知识……还有很长的路要走。

  Imports MySql.Data.MySqlClient

Public Class Reveal
    Public Property MyDataClass As SecurePasswordList
    Dim lastNameInput As String
    Dim firstNameInput As String
    Dim connStr As String = "server=0.0.0.0;user=johndoe;database=securePasswordList;port=3306;password=password;"
    Dim conn As New MySqlConnection(connStr)
    Dim SQL As String = "select password from securePasswordList.users where LAST_NAME like ' " & lastNameInput & "%'"
Dim cmd As MySqlCommand = New MySqlCommand(SQL, conn)

    Private Sub Reveal_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

    Private Sub firstName_TextChanged(sender As Object, e As EventArgs) Handles lastNameTextBox.TextChanged
        lastNameInput = lastNameTextBox.Text
        listBox.Items.Add(cmd)
    End Sub



    Private Sub lastName_TextChanged(sender As Object, e As EventArgs) Handles firstNameTextBox.TextChanged
        firstNameInput = firstNameTextBox.Text
    End Sub

    Private Sub listBox_SelectedIndexChanged(sender As Object, e As EventArgs) Handles listBox.SelectedIndexChanged

    End Sub
 End Class

Answer 1

您的问题之一是您实际上并未在任何地方执行 MySqlCommand。另外，我想向您指出 this link ，因为您在构建选择字符串的方式中在当前代码中存在潜在的安全问题。

这是一个如何找回密码的例子:

Private Function RetrievePassword(ByVal lastName As String) As String
    Using conn As New MySqlConnection(connStr)
        Using comm As New MySqlCommand(query, conn)
            comm.Parameters.AddWithValue("@LastName", lastName & "%'")

            Dim result As Object = comm.ExecuteScalar()

            If result Is Nothing Then
                handle as you like...
            End If

            Return result.ToString
        End Using
    End Using
End Function

query 将包含参数的占位符，如下所示:

    Private Const query As String =
         "select password from securePasswordList.users where LAST_NAME like @LastName"