show/hide label according to DataReader Results?
SqlCommand selectuser = new SqlCommand("select username,password from users where username = '" + TextBox1.Text + "' and password = '" + TextBox2.Text + "'", badersql);
    badersql.Open();
    SqlDataReader dr = selectuser.ExecuteReader();



    while (dr.Read())
    {
        if (dr["username"].ToString() == TextBox1.Text && dr["password"].ToString() == TextBox2.Text)
        {


        }
        else
        {
           Label1.Visible = true;

        }

    }

    dr.Close();

SqlCommand selectuser = new SqlCommand("select username,password from users where username = '" + TextBox1.Text + "' and password = '" + TextBox2.Text + "'", badersql);
        SqlDataReader dr = null;

        try
        {
            dr = selectuser.ExecuteReader();
            Label1.Visible = !dr.Read();
        }
        finally
        {
            if (dr != null)
                dr.Close();
        }