SqlDataReader not throwing an exception - ado.net

Question

I have method
public static SqlDataReader ExecuteReader(SqlCommand cmd, int level = 0)
{
SqlConnection conn = cmd.Connection;
SqlDataReader dr = null;
cmd.CommandTimeout = SqlConnectionTimeOut;
DateTime start = DateTime.Now;
DateTime end = new DateTime();
try
{
if (conn.State == System.Data.ConnectionState.Closed)
{
conn.Open();
}
dr = cmd.ExecuteReader();
}
catch (SqlException sqlex)
{
end = DateTime.Now;
TimeSpan requestDuration = end - start;
LoggerHelper.Info("SqlException - Execute reader duration before exception in milliseconds: " + requestDuration.TotalMilliseconds.ToString());
LoggerHelper.Error("Execute reader ", sqlex ,cmd);
if (sqlex.Number == 1205 && level <= 3) // will try to execute 3 times before throwing an Process deadlocked exception
{
LoggerHelper.Info(cmd.CommandText + " was a victim of deadlock. This was attempt " + (level + 1).ToString());
dr = ExecuteReader(cmd, level++);
}
else
{
throw new Exception("Execute reader ", sqlex);
}
// throw new Exception("Execute reader ", sqlex);
}
catch (Exception ex)
{
end = DateTime.Now;
TimeSpan requestDuration = end - start;
LoggerHelper.Info("Exception - Execute reader duration before exception in milliseconds: " + requestDuration.TotalMilliseconds.ToString());
LoggerHelper.Error("Execute reader ", ex, cmd);
throw new Exception("Execute reader ", ex);
}
return dr;
}
which is called from DAL
SqlDataReader reader = DataBridgeDb.ExecuteReader(TrisuraCommand);
datatable.Load(reader, LoadOption.OverwriteChanges, tablenames);
While debugging a SQL deadlock exception is properly thrown in ExecuteReader method.
But when I deploy or change connection string to staging database, exception is thrown in datatable.Load method.
Does anyone know why? I think it comes to database properties difference or SQL Server difference?

Answer 1

There is a problem on this line in the catch block:
dr = ExecuteReader(cmd, level++);
The ++ operator doesn't increment level until after the function call, so it passes 0 again the second time. And the third. And so on. You need this:
dr = ExecuteReader(cmd, level++);
As shown in this sample .Net Fiddle program:
https://dotnetfiddle.net/NWTZtS
I'm not sure how that causes the issue. I'd expect a StackOverflowException, the deadlock to eventually resolve, or an SqlException with a number other than 1205. But this is a bug, and I strongly suspect somehow tit is allows the method to eventually return a null value for the SqlDataReader object. At that point, of course the DataTable.Load() method will complain.