VB.NET 求助：数据库查询取不到数据

[_山枕寒流_]

Imports MySql.Data.MySqlClient
Public Class Form1
    '数据连接对象
    Dim con As New MySqlConnection
    Dim comm As New MySqlCommand

    '登录数据
    Dim user As String
    Dim pas As String
    REM 登录功能
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        '提取输入条件
        user = Username.Text
        pas = Password.Text
        Debug.Print(user + Chr(10) + pas)
        '查询语句
        Dim sql As String = "select * from userinfo where userName = '" & user & "'"
        Debug.Print(sql)
        comm = New MySqlCommand(sql, con)
        Dim da = New MySqlDataAdapter(sql, con)
        Dim dt = New DataSet()
        da.Fill(dt, "sql")
        MsgBox(dt.Tables("sql").Rows.Count)
        con.Close()


    End Sub
    '取消功能
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Username.Text = ""
        Password.Text = ""
    End Sub
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        '数据连接
        con.ConnectionString = "Server=127.0.0.1;UserID=root;Password=12345;Database=candy"
        con.Open()
        '数据连接状态判别
        If con.State = ConnectionState.Open Then
            Debug.Print("数据库连接成功！")
        Else
            Debug.Print("数据库连接失败！")
        End If
    End Sub

End Class

请问是哪里出了问题？

[wqnmlgj]

sql语句逻辑有问题吧，这样写不香吗？"select * from userinfo where userName = '" & Username.Text & "' and password = '" & Password.Text & "' 判断是否有返回值再执行下一步