Question

我在VB.NET中有一个函数，用于在启动主应用程序之前向MySQL数据库验证用户身份。这是函数的代码：

    Public Function authConnect() As Boolean
    Dim dbserver As String
    Dim dbuser As String
    Dim dbpass As String
    dbserver = My.Settings.dbserver.ToString
    dbuser = My.Settings.dbuser.ToString
    dbpass = My.Settings.dbpass.ToString
    conn = New MySqlConnection
    myConnString = "server=" & dbserver & ";" & "user id=" & dbuser & ";" & "password=" & dbpass & ";" & "database=rtadmin"
    Dim myCommand As New MySqlCommand
    Dim myAdapter As New MySqlDataAdapter
    Dim myData As New DataTable
    Dim myDataReader As New MySqlDataReader
    Dim query As String

    myCommand.Parameters.Add(New MySqlParameter("?Username", login_usr_txt.Text))
    myCommand.Parameters.Add(New MySqlParameter("?Password", login_pass_txt.Text))
    query = "select * from users where user = ?Username and passwd = ?Password"
    conn.ConnectionString = myConnString
    Try
        conn.Open()
        Try
            myCommand.Connection = conn
            myCommand.CommandText = query
            myAdapter.SelectCommand = myCommand
            myDataReader = myCommand.ExecuteReader
            If myDataReader.HasRows() Then
                MessageBox.Show("You've been logged in.", "RT Live! Information", MessageBoxButtons.OK, MessageBoxIcon.Information)
            End If
        Catch ex As Exception

        End Try
    Catch ex As Exception

    End Try
End Function

该功能尚未完成，在启动应用程序之前还需要完成其他一些事情，因为我使用MessageBox来显示登录尝试的结果。

我得到的错误如下：

错误1'MySql.Data.MySqlClient.MySqlDataReader.Friend Sub New（cmd As MySql.Data.MySqlClient.MySqlCommand，statement as MySql.Data.MySqlClient.PreparableStatement，behavior As System.Data.CommandBehavior）'无法访问在这种情况下，因为它是'朋友'。 C：\ Users \ Mario \ documents \ visual studio 2010 \ Projects \ Remote Techs Live！\ Remote Techs Live！\ Login.vb 43 13 Remote Techs Live！

有什么想法吗？

Answer 1

尝试创建一个MySqlDataReader然后扔掉它是没有意义的！

首先，您要尝试创建阅读器：

    Dim myDataReader As New MySqlDataReader

然后，当你这样做时，你会尝试扔掉它：

    myDataReader = myCommand.ExecuteReader

只需从初始声明中删除New即可。我怀疑MySqlDataReader的构造函数不能公开访问。

Answer 2

您可以尝试.AddWithValue而不是.Add。

例如：

cmd.Parameters.AddWithValue("?Username", login_usr_txt.Text)

MySqlDataReader在构建时给出错误

2 个答案: