Error = trying to read when no Data present.  code below

Programmers do not like to check for errors but we need to. Your cs.Open(); should be done in try ... catch blocks. Just to be sure everything is working, you can check to ensure that cs.State is System.Data.ConnectionState.Open. Also many programmers will say to use SqlDataReader in a using block. Others have answered the question about why you are getting the current error.

The error message “trying to read when no Data present” is likely due to the fact that the SQL query did not return any data. In your code, you’re trying to read data from the SqlDataReader without checking if there are any rows returned by the query.

You can avoid this error by checking if there are any rows in the SqlDataReader before trying to read data. Here’s how you can modify your code:

private void getLoggedOnID()
{
    dsUser.Clear();
    try
    {
        string s2 = tBoxUID.Text;
        string s1 = "SELECT * FROM tbUser WHERE UID = \'" + s2 + "\'";
        MessageBox.Show("s1 = " + s1);

        SqlCommand cmd = new SqlCommand(s1, cs);
        cs.Open();
        SqlDataReader reader = cmd.ExecuteReader();

        if (reader.HasRows)
        {
            reader.Read();
            usr.LoggedOnID = reader.GetInt32(0);
            usr.UID = reader.GetString(1);
            usr.PWD = reader.GetString(2);
            usr.PWDHint = reader.GetString(3);
            usr.DisplayName = reader.GetString(4);
            usr.Email = reader.GetString(5);
            usr.IsLoggedOn = true;
        }
        else
        {
            MessageBox.Show("No data found for the given UID.");
        }

        reader.Close();
        cs.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error: " + ex.Message);
    }
}

This code checks if the SqlDataReader has any rows using the HasRows property. If it does, it reads the data. If not, it shows a message saying “No data found for the given UID”. This should prevent the error you’re seeing. Please replace the MessageBox.Show("Error: " + ex.Message); with your own error handling logic. Remember, it’s always a good practice to handle exceptions that might occur during database operations.

Thanks

Check reader has data or not using HasRows property,

           dsUser.Clear();
           try
           {
               string s2 = tBoxUID.Text;
               string s1 = "SELECT * FROM tbUser WHERE UID = \'" + s2 + "\'";
               MessageBox.Show("s1 = " + s1);

               SqlCommand cmd = new SqlCommand(s1, cs);
               cs.Open();
               SqlDataReader reader = cmd.ExecuteReader();
              if (reader.HasRows)
              {
               usr.LoggedOnID = reader.GetInt32(0);
               usr.UID = reader.GetString(1);
               usr.PWD = reader.GetString(2);
               usr.PWDHint = reader.GetString(3);
               usr.DisplayName = reader.GetString(4);
               usr.Email = reader.GetString(5);
               usr.IsLoggedOn = true;

               reader.Close();
               cs.Close();
               }
             }