Entity Framework asp.net mvc5- Cannot convert lambda expression to type 'string' because it is not a delegate type

Question

I am trying to do

IList<Sth> sths= Context.Sth.Where(g => g.IsX == true && g.Y.Name== "name").ToList();  //here it successfully compares  g.Y.Name
            foreach (Sth g in sths)
            {
                Context.Entry(g).Collection(g=>g.Y).Load(); //the exception is thrown here
                this.mylist.Add(g.Y.Id);
            }

I already tried

using System.Data.Entity;
using System.Linq;

.

Apparently g.Y is not ICollection<>. Use either .Reference method (instead of .Collection) or better why not eager load it in the main query with Include. — Ivan Stoev
– Ivan Stoev, Commented Dec 17, 2018 at 11:13
You can include sub entities on the main query using Include learn.microsoft.com/en-us/ef/ef6/querying/related-data — Ahmed Ghoniem
– Ahmed Ghoniem, Commented Dec 17, 2018 at 11:14

DavidG · Accepted Answer · 2018-12-17 11:19:10Z

2

g.Yis not a collection otherwise you wouldn't be able to call g.Y.Name on the first line. So you should either use Reference instead of collection, or preferably use Include instead. For example:

IList<Sth> sths = Context.Sth
    .Where(g => g.IsX == true && g.Y.Name== "name")
    .Include(g => g.Y)
    .ToList(); 

this.mylist.AddRange(sths.Select(g => g.Y.Id);

But, if all you are trying to do it get the Id property, then you can just do that:

this.mylist.AddRange(Context.Sth
    .Where(g => g.IsX == true && g.Y.Name== "name")
    .Select(g => g.Y.Id));

answered Dec 17, 2018 at 11:19

DavidG

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1 Comment

thestruggleisreal Over a year ago

thanks! But than, I had to change the IList to IQueryable :)

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