Question

The same query works fine in SQL Server. I need it to return all rows read from the DB table in c#.

SqlCommand cmd = new SqlCommand();
cmd.Connection = connection;
cmd.CommandText = @"SELECT TypeName, Sum(HitNo) FROM TypeHit GROUP BY TypeName";

SqlDataReader sdr = cmd1.ExecuteReader();
sdr.Read();

if (sdr.HasRows)
{
   while (sdr.Read())
   {
       TextBox1.Text = sdr.GetString(0) +" at " + sdr.GetInt32(1);
   }
}

Answer 1

Why are you using sdr.Read(), that will advance the reader to the next block of data?

DataReader.Read Method

You’re also overwriting the TextBox‘-Text property for every record in the reader since while (sdr.Read()) is a loop.

using(SqlDataReader sdr = cmd1.ExecuteReader())
{
        if (sdr.HasRows)
        {
            while (sdr.Read())
            {
                TextBox1.Text += sdr.GetString(0) + " at " + sdr.GetInt32(1) + Environment.NewLine;
            }
        }
        else
        {
            TextBox1.Text = "No rows found.";
        }
}

Retrieving Data Using a DataReader (ADO.NET)