Retrieve Tasks by Employee
Remove the additional ()s in the statusFilter and employeeFilter lines as they are unnecessary.
Indent the statusFilter and employeeFilter lines so that they are symmetrical with the search lines.
Change search to be searchTerm as it is more specific.  search by itself could mean anything like a stored query, a boolean value, etc.
As per Magus' comment you can change t to task since it is more clear and will not add space that starts pushing statements across extra lines.




var tasks = db.Tasks
  .Include(task =&gt; task.Employee)
  .Include(task =&gt; task.Status)
  .Where(task =&gt;
    (
      searchTerm == null || 
      task.Employee.FirstName.Contains(searchTerm) ||
      task.Employee.LastName.Contains(searchTerm) ||
      task.Employee.EmployeeId.Contains(searchTerm)
    ) &amp;&amp;
    (
      statusFilter == null || 
      task.StatusId = statusFilter.Value
    ) &amp;&amp;
    (
      employeeFilter == null || 
      task.EmployeeId == employeeFilter
    )
);