Add Exists and ExistsAsync like Find and FindAsync

[nrhoffmann]

I am trying to check if an entity exists given a Type and key.

I'd like to have a method Exists and ExistsAsync that return a boolean. Currently, I use Find and FindAsync, but since I don't need the object returned from the database, its a waste, especially for big objects.

[roji]

That should be trivial to implement in your project as an extension method over DbSet, which just does a LINQ query (e.g. context.Blogs.Any(b => b.Id == someId).

The reason Find/FindAsync exist as special methods is because they look inside EF's change tracker before actually contacting the database, so they save a database roundtrip if the entity instance is already tracked.

[nrhoffmann]

How would you recommend getting a DbSet from typeof(TEntity)? I am using Find because I don't need to know the type or the key property name/s.

[ajcvickers]

Note from triage: we will not make this change. Options are:

• Implement specific, typed Exists methods for the entity types you have
• Continue to use Find for this, and discard the allocated instances
• Implement a non-type-specific Exists method by copying the code for Find. This could be made easier by Add key values sugar #7391.