linq-to-sql null或默认值

Question

I have a query that looks like this:

var TheQuery = (from....
               where x.TheDate >= StartDate && x.TheDate <= EndDate
               select new MyModel()
               {
                   Total = (int?)x.Count() ?? 0,
                   ....
               }).Single();

Basically, I'm querying a number of records based between 2 dates. If for the date there are 0 values, it returns 0 as the Total. However, if there are no values at all, it returns null and crashes. I could add .SingleOrDefault() but it would return null instead of MyModel populated with a 0. The property Total is defined as an int.

How can I solve this?

Thanks

Answer 1

Count has an overload with a predicate, and returns 0 when no item matches the predicate

 var result = new MyModel {
                          Total = <yourDataSource>
                            .Count(x.TheDate >= StartDate && x.TheDate <= EndDate)
                          };

Answer 2

if(TheQuery !=null || TheQuery .Count()>0){
 //do something you wanna do

}

or

 var v = TheQuery.ToList();

now check

if (v.Count > 0)

Answer 3

You should opt for:

int count = (from x in ...
where x.TheDate >= StartDate && x.TheDate <= EndDate
select c).Count();

That's what you want.

Answer 4

var TheQuery = (from....
               where x.TheDate >= StartDate && x.TheDate <= EndDate
               select new MyModel()
               {
                   Total = (int?)x.Count() ?? 0,
                   ....
               }).DefaultIfEmpty(0).Single()'