C# allow nullable value get from EF

You can get value from Entity framework which can allow null able and you can also perform filtering in your query.

  private static IQueryable<EmployeeInformation> ReportFilteringEmployeeInformations(Guid factoryId, Guid departmentId, Guid designationId, string empId,  
     string empName, Guid sectionId, Guid categoryEmpId, int? CategoryTypeID, Guid categorySalaryID, Guid blockID,string cardNo, PayrollEntities context)  
     {  
       var query =  
         from emp in context.vw_PIS_TblEmployeeGenInfo  
         join des in context.vw_PIS_TblEmployeeDesignation on emp.GDesignationInfoID equals des.GDesignationInfoID into  
           des_J  
         join dept in context.vw_PIS_tblDepartment on emp.GDepartmentID equals dept.GDepartmentID into dept_J  
         join sec in context.vw_PIS_TblSection on emp.SectionID equals sec.SectionID into sec_J  
         from des1 in des_J.DefaultIfEmpty()  
         from dept1 in dept_J.DefaultIfEmpty()  
         from sec1 in sec_J.DefaultIfEmpty()  
         select new EmployeeInformation  
         {  
           GEmployeeGenInfoID = emp.GEmployeeGenInfoID,  
           GFactoryID = emp.GFactoryID ?? Guid.Empty,  
           GDepartmentID = emp.GDepartmentID ?? Guid.Empty,  
           GDesignationInfoID = emp.GDesignationInfoID ?? Guid.Empty,  
           GSectionID = emp.SectionID ?? Guid.Empty,  
           GEmployeeCatID = emp.GEmployeeCatID ?? Guid.Empty,  
           CategoryEmpID = emp.CategoryEmpID,  
           GCategorySalaryID = emp.CategorySalaryID ?? Guid.Empty,  
           BlockID = emp.BlockID ?? Guid.Empty,  
           StrEmpID = emp.StrEmpID,  
           StrEmpCardNo = emp.StrEmpCardNo,  
           StrEmpName = emp.StrEmpName,  
           dtJoiningDate = emp.dtJoiningDate,  
           DtConfirmationDate = emp.DtConfirmationDate ?? DateTime.MaxValue,  
           strDesignationName = des1.StrDesignationName,  
           strDepartmentName = dept1.StrDepartmentName,  
           SectionName = sec1.SectionName,  
           CategoryTypeID = emp.CategoryTypeID,  
           GSalaryIncrementID = Guid.Empty,  
           dtIncrementDate = null,  
           dtEffectiveDate = null  
         };  
       /*********************************************************************/  
       // FILTER / where clause   
       if (factoryId != Guid.Empty)  
         query = query.Where(x => x.GFactoryID == factoryId);  
       if (departmentId != Guid.Empty)  
         query = query.Where(x => x.GDepartmentID == departmentId);  
       if (designationId != Guid.Empty)  
         query = query.Where(x => x.GDesignationInfoID == designationId);  
       if (!String.IsNullOrEmpty(empId))  
         query = query.Where(x => x.StrEmpID == empId);  
       if (!String.IsNullOrEmpty(empName))  
         query = query.Where(x => x.StrEmpName == empName);  
       if (sectionId != Guid.Empty)  
         query = query.Where(x => x.GSectionID == sectionId);  
       if (categoryEmpId != Guid.Empty)  
         query = query.Where(x => x.CategoryEmpID == categoryEmpId);  
       if (categorySalaryID != Guid.Empty)  
         query = query.Where(x => x.GCategorySalaryID == categorySalaryID);  
       if (blockID != Guid.Empty)  
         query = query.Where(x => x.BlockID == blockID);  
       if (!String.IsNullOrEmpty(cardNo))  
         query = query.Where(x => x.StrEmpCardNo == cardNo);  
       if (CategoryTypeID != null && CategoryTypeID != 0)  
         query = query.Where(x => x.CategoryTypeID == CategoryTypeID);  
       return query;  
     }