Question

I’m trying to extend a method that already has a return type. For example:

IQueryable<int> GetCategoryIds()

So, I can use this as follows:

IQueryable<int> categories = GetCategoryIds();

And I’m currently doing:

IQueryable<int> categories = GetCategoryIds().Select(c => new Client() { ClientId == c.clientId });

This works, but I don’t want to do that Select statement. I’d rather do an extension method that excepts a type so I can use Reflection in the extension method to determine the type etc. and return the results according. The extension method would be something like:

public static IQueryable<T> LovelyExtension(this T objectType, int clientId)

Then I can use this extension like (hopefully):

IQueryable<int> categories = GetCategoryIds().LovelyExtension<int>(1);

Is this possible? When I tried it, I got an error because the GetCategoryIds return type wasn’t the same as the extension method. But, this works with the Select statement.

Answer 1

You do not need to write an extension on Type (your example is not doing it either). You need an extension on IQueryable<T>. You can do it like this:

public static IQueryable<T> LovelyExtension<T>(this IQueryable<T> input, int clientId) {
    Type inputType = typeof(T);
    // Here you can use reflection if you need to: inputType corresponds to the type of T
    // Create an instance of IQueryable<T>, and return it to the caller.
}