What happens when I'm casting an Linq to Entity query to ObjectQuery?

Question

Hi,

Simple question - what does this actually do?

var oq = (ObjectQuery<TEntity>)L2EQuery;
return ExecuteFirstorDefault<TEntity>(oq, MergeOption.AppendOnly);

It's partly from the book Programming Entity Framework, by Julia Lerman.

Answer 1

The cast itself does nothing more than check the type. Since your query is of type ObjectQuery<TEntity>, it succeeds. I presume ExecuteFirstOrDefault requires an argument of that type, hence the cast.