Index Outside the bounds of array

Hello,

I have written a code to create the login module of a system. I dont know what is the problem, i have done the exact code before and it worked but this time its giving an exception  "Index outside the bounds of array".

The code is

string login = "select Password from UserInfo where Username = "+tbx_username.Text+"'";
           
            conn.Open();
            SqlCommand cmd = new SqlCommand(login, conn);
            SqlDataReader reader = null;
             reader = cmd.ExecuteReader();           
                if (reader.Read())
                {

                  if (tbx_password.Text == reader.GetValue(1).ToString())
                    {
                        MessageBox.Show("welcome " + tbx_username.Text + "");
                    }
                }
                else
                {
                    MessageBox.Show("invalid username or password!");
                }
          
            conn.Close();

Any urgent help will be very much appreciated!

Regards!