vb.net - クエリ式の文字列の構文エラー

Question

「クエリ式 'Username = user' の文字列に構文エラーがあります」というエラーが表示されます。問題は「me.Username.tag」にあると思いますが、動かなくなりました。

conn = New OleDbConnection(Get_Constring)
        conn.Open()
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = "select Username, fname,  lname, mname, [password], [level], Question, answer from Instructor where Username= '" & Me.txtusername.Tag

        dr = cmd.ExecuteReader
        If dr.HasRows Then
            While dr.Read
                Me.txtusername.Tag = dr("Username")
                Me.txtfname.Text = IIf(Not IsDBNull(dr("fname")), dr("fname"), "")
                Me.txtlname.Text = IIf(Not IsDBNull(dr("lname")), dr("lname"), "")
                Me.txtinitial.Text = IIf(Not IsDBNull(dr("mname")), dr("mname"), "")
                Me.txtpassword.Text = IIf(Not IsDBNull(dr("password")), dr("password"), "")
                Me.lbllevel.Text = IIf(Not IsDBNull(dr("level")), dr("level"), "")
                Me.txtusername.Text = IIf(Not IsDBNull(dr("Username")), dr("Username"), "")
                Me.cmbquestion.Text = IIf(Not IsDBNull(dr("Question")), dr("Question"), "")
                Me.txtanswer.Text = IIf(Not IsDBNull(dr("answer")), dr("answer"), "")
            End While
        End If