小编use*_*077的帖子

我需要能够在Linq查询中具有可选参数,或者如果需要从查询中删除该可选参数,则能够将查询分配给类似IF的var.

如果我在IF语句中设置查询var,那么当我尝试循环时,它告诉我var在上下文中不存在.

if (whichGroup == "All")
        {
            var listOppLineData = (from o in db.opportunity_vws
                                   where o.fiscal_yr_and_qtr == qtr
                                   select o
                                  );
        }
        else
        {
            var listOppLineData = (from o in db.opportunity_vws
                                   where o.fiscal_yr_and_qtr == qtr && o.Group == whichGroup
                                   select o
                                  );
        }

        foreach (var data in listOppLineData)  //listOppLineData doesn't exist here
        {

我需要在我认为的IF语句之前设置var,但我不知道将它设置为什么.

var listOppLineData = ""; // gives me 
Cannot implicitly convert type 'System.Linq.IQueryable<Forecast.Models.opportunity_vw>' to 'string'

IQueryable listOppLineData = new IQueryable(); //gives me
        Cannot create an instance of …