restfly.blogg.se

This optimization should only be used if the function can only return null when it's parameters are null. The second query doesn't need to re-evaluate the function itself to test its nullability. When issuing the following queries: var quer圓 = (e => context.ConcatStrings(e.Url, e.Rating.ToString()) != "") Į => context.ConcatStringsOptimized(e.Url, e.Rating.ToString()) != "") The second function is configured to take advantage of the nullability propagation optimization, providing more information on how the function behaves around null parameters. The first function is configured in the standard way. This function definition can now be associated with user-defined function in the model configuration: modelBuilder.HasDbFunction(typeof(BloggingContext).GetMethod(nameof(ActivePostCountForBlog), new ),ī.HasParameter("prm1").PropagatesNullability() ī.HasParameter("prm2").PropagatesNullability() In the example, the method is defined on DbContext, but it can also be defined as a static method inside other classes. If the arguments can be translated, EF Core only cares about the method signature. The method will not be invoked client-side, unless EF Core can't translate its arguments. The body of the CLR method is not important. To use this function in EF Core, we define the following CLR method, which we map to the user-defined function: public int ActivePostCountForBlog(int blogId) Next, create the user-defined function CommentedPostCountForBlog, which returns the count of posts with at least one comment for a given blog, based on the blog Id: CREATE FUNCTION int) To illustrate how user-defined function mapping works, let's define the following entities: public class BlogĪnd the following model configuration: modelBuilder.Entity()īlog can have many posts and each post can have many comments.

When translating the LINQ query to SQL, the user-defined function is called instead of the CLR function it has been mapped to. To do that, the functions need to be mapped to a CLR method during model configuration. EF Core allows for using user-defined SQL functions in queries.