have a read of this
c# - Visual Studio during Debugging: The function evaluation requires all threads to run - Stack Overflow
without knowing where the exception is raised I can't suggest anything other than having a read of the above.
Plus I would also change the code to something like the following
var foundEmployees = db.Emps.Where(s => s.Name.Contains(Search));
if(foundEmployees == null) ModelState.AddModelError("Name"," No records found");