Using Func<> in Entity Framework Query

Question

I have the following Entity Framework query:

Func<Company, bool> filter;
if (officeId != 0)
    filter = company => !company.IsDeleted && company.OfficeCompanies.Any(c => c.OfficeId == officeId);
else
    filter = company => !company.IsDeleted;

var companies = from c in Repository.Query<Company>()
                where filter(c) &&
                    (relationshipTypes.Count() == 0 || relationshipTypes.Any(r => r == c.TypeEnumIndex)) &&
                    c.Description.Contains(term)
                orderby c.Description
                select new JqueryUiAutoCompleteItem
                {
                    label = c.Description,
                    value = SqlFunctions.StringConvert((double)c.Id)
                };

It gives me the error:

The LINQ expression node type 'Invoke' is not supported in LINQ to Entities.

If I remove the reference to filter() in the main body of the query, there is no error.

I understand the meaning of this error: I am using code that cannot be converted into SQL. But what is there about my filter() that cannot be converted to SQL?

Answer 1

You need to switch the Func to an Expression, then pass that expression to a Where directly in LINQ fluent syntax. I don't think there's a way to use the expression in query syntax.

Expression<Func<Company, bool>> filter; //<-- changed type
if (officeId != 0)
    filter = company => !company.IsDeleted && company.OfficeCompanies.Any(c => c.OfficeId == officeId);
else
    filter = company => !company.IsDeleted;

var companies = from c in Repository.Query<Company>().Where(filter) // <-- changed syntax
                where (relationshipTypes.Count() == 0 || relationshipTypes.Any(r => r == c.TypeEnumIndex)) &&
                    c.Description.Contains(term)
                orderby c.Description
                select new JqueryUiAutoCompleteItem
                {
                    label = c.Description,
                    value = SqlFunctions.StringConvert((double)c.Id)
                };