CODEWITHSUNDEEP
c#linq
elite5472
elite5472

Reputation: 2184

Cast a Linq result set to an interface

I have the following query:

var result = context.BEntries
    .Where(x => x.a == "a")
    .Select(x => new MyClass()
    {
        a = x.a
    }).ToList();

I get a result of type List<MyClass>. However, I must return IEnumerable<IMyclass>. How do I cast this to its generic definition?

Upvotes: 3

Views: 1432

Answers (4)

Douglas
Douglas

Reputation: 54887

If you're using an older version of C# that does not support covariance, you can use Cast:

var result = context.BEntries
                    .Where(x => x.a == "a")
                    .Select(x => new MyClass() { a = x.a })
                    .AsEnumerable()
                    .Cast<IMyClass>();

Upvotes: 3

SLaks
SLaks

Reputation: 887451

You don't need to.

IEnumerable<T> is covariant; List<MyClass> is implicitly convertible to IEnumerable<IMyClass>.

.Net 3.5 does not use covariance, so you'll need to cast it yourself.

You can either call .Cast<IMyClass>() or cast the select expression to IMyClass so that the query returns IMyClass in the first place.

Upvotes: 7

Sukram
Sukram

Reputation: 466

Do not use var, simple define a List or IEnumerable of your interface

Upvotes: 0

BenjaminPaul
BenjaminPaul

Reputation: 2931

As long as MyClass implements IMyClass this should be fine as it is.

Upvotes: 0

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