How to fetch particular coloumn using SQL stored procedure in WPF C#

private void SignIn_Click(object sender, RoutedEventArgs e)
      {
          try
          {
              if (isValid())
              {
                  SqlConnection conn = new SqlConnection(ConnectionString);
                  conn.Open();
                  SqlCommand cmd = new SqlCommand("add_profile", conn);
                  //cmd.CommandType = CommandType.StoredProcedure;
                  cmd.Parameters.AddWithValue("@username", txtUsername.Text);
                  cmd.Parameters.AddWithValue("@password", txtpassword.Password);
                  cmd.Parameters.AddWithValue("@selectusertype", cmboSelectusertype.Text);
                 // conn.Open();
                  cmd.ExecuteNonQuery();
                  conn.Close();
                  SqlDataAdapter da = new SqlDataAdapter(cmd);
                  DataTable dt = new DataTable();
                  da.Fill(dt);
                  if (dt.Rows.Count > 0)
                  {
                      refresh();
                      Employee emp = new Employee();
                      emp.ShowDialog();
                  }
              }
          }
          catch (SqlException ex)
          {
              MessageBox.Show(ex.Message);
          }

      }

public bool isValid()
       {
           if (string.IsNullOrEmpty(this.txtUsername.Text) | string.IsNullOrEmpty(this.txtpassword.Password))
           {
               MessageBox.Show("provide User Name and Password");
           }

           else if (string.IsNullOrEmpty(cmboSelectusertype.Text))
           {
               MessageBox.Show("Select User Type");
           }
           return true;
       }