Error : Sequence contains no elements when you execute query that return null

In this statement if Trans.param1== param1Value returns nothing, you will hit the error above.

Class1 objClass1 = _db.Class1.First(Trans => Trans.param1== param1Value);

To prevent this, you need to use 'FirstOrDefault' instead

Class1 objClass1 = _db.Class1.FirstOrDefault(Trans => Trans.param1== param1Value);

Sharepoint Timer Error

After you deploy the solution file and when you try to deploy the solution, you see the following error message.

You should check your [Windows Sharepoint Service Administration] if it is activated. !!! After you activated the service, make sure you run the command below to execute the timer job directly instead of wasting your time to wait for sharepoint to pick up the job.

STSADM –O execadmsvcjobs

The timer job for this operation has been created, but it will fail because the administrative service for this server is not enabled. If the timer job is scheduled to run at a later time, you can run the jobs all at once using stsadm.exe -o execadmsvcjobs. To avoid this problem in the future, enable the Windows SharePoint Services administrative service, or run your operation through the STSADM.exe command line utility