从 VB.Net 读取和写入 SQL 信息

Question

我有一个将我的 vb.net 项目链接到一个唯一的 SQL 数据库，该数据库包含一个预定义的电子邮件地址列表。我的 vb 表单包含一个“名字”、“姓氏”和“电子邮件”文本框。

如何编程 vb.net 以在数据库中的“电子邮件”文本框中定位文本，并将 firstname 和 lastname 文本框值添加到与定位的电子邮件字段相同的行中的相应列中？ （填补空白）

到目前为止我的代码：

' Initiate SQL Connection for db4free.net on port: 3306
    MySqlConnection = New MySqlConnection
    MySqlConnection.ConnectionString = "server=db4free.net; Port=3306; user id=username; password=password; database=databasename"
    Try
        MySqlConnection.Open()
    Catch ex As Exception
        MsgBox("The server could not be reached, check that you have internet connectivity and try again.", MsgBoxStyle.Critical, "Connection Error")
    End Try

        --- SQL DATABASE CONNECTION --- '
        Dim Myadaptor As New MySqlDataAdapter
        Dim sqlquery = "SELECT * FROM registration WHERE email='" & emailTextBox.Text & "';"
        Dim command As New MySqlCommand
        command.Connection = MySqlConnection
        command.CommandText = sqlquery
        Myadaptor.SelectCommand = command
        Dim Mydata As MySqlDataReader
        Mydata = command.ExecuteReader

        ' SQL Entry Validation
        If Mydata.HasRows = 0 Then
            MsgBox("Please enter a valid E-Mail address", MsgBoxStyle.Critical, "Invalid Details")
        Else
           --- THE ANSWER TO MY QUESTION (write firstname and lastname into row based on email) ---

提前谢谢你，（我才刚开始学习 SQL）。

Answer 1

你会想做这样的事情：

If Mydata.HasRows = 0 Then
    MsgBox("Please enter a valid E-Mail address", MsgBoxStyle.Critical, "Invalid Details")
    Mydata.Close()
Else
    Mydata.Close()
    Dim command As New MySqlCommand
    command.Connection = MySqlConnection
    command.ConnectionText = "UPDATE `registration` SET `firstname` = @firstname,`lastname` = @lastname WHERE `email` = @email"
    command.Prepare()
    command.Parameters.AddWithValue("@firstname", firstnameTextBox.Text)
    command.Parameters.AddWithValue("@lastname", lastnameTextBox.Text)
    command.Parameters.AddWithValue("@email", emailTextBox.Text)
    command.ExecuteNonQuery()
End If

您可能需要调整 SQL 或对 UI 元素的引用以匹配您的设置。

我还将参数绑定到 SQL 中，而不是通过连接参数来创建字符串，以防止SQL Injection。