Does explicit client evaluation of where clause require AsEnumerable?-CodePudding

StandardizeUrl is function written in c#. Suppose it is used in the select query then the function is applied in memory after the data is returned by sql - example:

var blogs = context.Blogs
    .OrderByDescending(blog => blog.Rating)
    .Select(
        blog => new { Id = blog.BlogId, Url = StandardizeUrl(blog.Url) })
    .ToList();

This question is about using a custom c# function in WHERE clause. The below return runtime exception:

var blogs = context.Blogs
    .Where(blog => StandardizeUrl(blog.Url).Contains("dotnet"))
    .ToList();

Solution is given here: Link- https://docs.microsoft.com/en-us/ef/core/querying/client-eval#explicit-client-evaluation

var blogs = context.Blogs
    .AsEnumerable()
    .Where(blog => StandardizeUrl(blog.Url).Contains("dotnet"))
    .ToList();

Why does the link says we can either use AsEnumerable or ToList. For example if I don't use AsEnumerable then it gives an error.

CodePudding user response：

The point is that you get "client evaluation" with methods like AsEnumerable() or ToList() before using the Where() call. That way the data is (fully) transferred to the client (your C# application) and then filtered on the client side, where you have access to your StandardizeUrl() method. The documentation does not talk about the ToList() after the Where() call.