使用Entity Framework获取列的总和

Question

我想使用实体框架实现以下SQL语句：

select coalesce(SUM(cdin_ActMortgageAmnt), 0) 
from CRM.dbo.CDIndex,CRM.dbo.company  
where comp_companyid = cdin_companyid 
  and comp_idcust like '%10319%' 
  and cdin_Deleted is null 
  and cdin_startunstufdate is not null 
  and cdin_Status = 'InProgress'

我试图获得cdin_ActMortgageAmnt：

的总和

Company c = db.Companies.Find(750);  

var CGP = (from cd in db.CDIndexes  
           join com in db.Companies on cd.cdin_CompanyId equals com.Comp_CompanyId  
           where com.Comp_IdCust == c.Comp_IdCust &&  
                 cd.cdin_Deleted == null &&  
                 cd.cdin_startunstufdate == null &&  
                 cd.cdin_Status == "InProgress"  
           select new  
                 {  
                     act = cd.cdin_ActMortgageAmnt == null ? 0 : cd.cdin_ActMortgageAmnt 
                 }  
          );  

var query = CGP.Sum(x => x.act);  
lblSum.Text = query.ToString();  

但是在跟踪时查询返回null ...