I have resolve it my self. only adding a single function "AsEnumerable()" before Select function. :)
var resultDistrictServiceLogReportDetails =
_sOAPNoteRepository.GetAll()
.Where(i => i.CreatedBy == therapist.Id &&
i.DateofService < searchendDate &&
i.DateofService >= searchstartDate &&
i.TimeLogClientList.TimeLog.TimeLogActivity.SOAPReq.Value &&
i.Employee.Service != null &&
i.TimeLogClientList.TimeLog.TimeLogContractSite.ContractType
.ContractType1.ToLower().Equals(Utilities.SCHOOLDISTRICT.ToLower()) &&
i.TimeLogClientList.TimeLog.Errors == null && i.TimeLogClientList.TimeLog.Rejected == null &&
(i.TimeLogClientList.TimeLog.Void == null || !i.TimeLogClientList.TimeLog.Void.Value)).AsEnumerable()
.Select(i => new
{
i.Client,
i.TimeLogClientList.Grade,
i.DateofService,
i.Time,
i.TimeLogActivity.ActivityDesc,
i.TimeLogClientList.TimeLog.TimeLogCategory.Category,
i.ActivityId,
i.ContractSiteId,
i.TimeLogContractSite.ContractSite,
i.TimeLogClientList.TherapistId,
ServiceId = i.Employee.ServiceId,
i.SNote,
i.ONote,
i.ANote,
i.PNote,
SignedDate = i.TimeLogClientList.TimeLog.SignedDate,
i.Location,
i.Employee,
ID = i.CreatedBy,
i.TimeLogClientList.TimeLog.ElapsedTime,
i.SupSignedBy,
i.SupSignedDate,
i.Employee3,
cptcode = _activityCPTCodeRepository.GetAll()
.Where(x => x.ActivityId == i.TimeLogActivity.Id && x.ServiceId == i.Employee.Service.Id)
.Select(x => x.CptCode).FirstOrDefault().ToString()
}).ToList();