Getting Timeout on stored procedure call

Question

I have a stored procedure which works fine when executed manually but when it is called on the code it return a Null Reference Exception because of a TimeOut. Here's the code:

private DataTable GetProcedure(DateTime dtStart, DateTime dtEnd) {
        DataTable dt = new DataTable();
        SqlDataReader reader;

        string cs = //Connection String, it works everywhere, no need to put the code.
        SqlConnection sqlConnection = new SqlConnection(cs);
        string cmdText = "ProcedureName";
        SqlCommand cmd = new SqlCommand(cmdText, sqlConnection);
        cmd.CommandType = CommandType.StoredProcedure;

        SqlParameter pFechaInicio = new SqlParameter("@dtStart", dtStart);
        SqlParameter pFechaFin = new SqlParameter("@dtEnd", dtEnd);
        cmd.Parameters.Add(pFechaInicio);
        cmd.Parameters.Add(pFechaFin);

        sqlConnection.Open();

        reader = cmd.ExecuteReader(); //NULL REFERENCE EXCEPTION HERE

        dt.Load(reader);

        sqlConnection.Close();

        return dt;
}

I made a manual call to the stored procedure with the exact same parameters and it worked fine (The stored procedure returns a 3 row / 2 column result with no NULLs whatsoever.

Even more, this error started happening 1 month ago but the program has been running for 6 months flawlesly.

EDIT: Here's some info on the SP:

SP header:

ALTER PROCEDURE  [dbo].[SPName]
        @dtStart datetime, @dtEnd datetime
AS
BEGIN
    SET NOCOUNT ON;  

select column1 as Name1, column2 as Name2
/* doesn't matter */

END

The specific result I'm getting when I execute the SP manually is:

column1     column2
1.0000000   105.426890
2.0000000   96.316330
3.0000000   82.849690

And here's the whole error code:

en System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   en System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   en System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   en System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   en System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
   en System.Data.SqlClient.SqlDataReader.get_MetaData()
   en System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   en System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
   en System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)
   en System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   en System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   en System.Data.SqlClient.SqlCommand.ExecuteReader()
   en BACK.OFERTAS.COBERTURAS.PRECIOS._01._00.StartJob.GetProcedure(DateTime dtStart, DateTime dtEnd) en C:\Users\Dell\Documents\BACK.OFERTAS.COBERTURAS.PRECIOS.01.00\StartJob.cs:línea 278
   en BACK.OFERTAS.COBERTURAS.PRECIOS._01._00.StartJob.Start() en C:\Users\Dell\Documents\BACK.OFERTAS.COBERTURAS.PRECIOS.01.00\StartJob.cs:línea 176

Re-Reading the whole stackTrace it seems like a Timeout? How is that even possible, there SP is executed in less than 1 sec.

Answer 1

I've solved it changing the TimeOut time of the procedure (which was of 30 secs by default).

This happens because it isn't the same to execute a SP directly on the server than in the job.