Get methodinfo for Enumerable.DefaultIfEmpty

I'm building some Linq Expression and trying to get hold of Meth开发者_JAVA百科odInfo for IEnumerable.DefaultIfEmpty (http://msdn.microsoft.com/en-us/library/bb360179.aspx). What seemed to be an easy task but I'm clueless to why it's not working.

typeof(Enumerable).GetMethod("DefaultIfEmpty", new[] { typeof(IEnumerable<>) });

typeof(Enumerable).GetMethod("DefaultIfEmpty", new[] { typeof(IEnumerable<>).MakeGenericType(typeof(WorkitemListModel)) });

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Getting generic methods is a pain, to be honest. I don't know of a better way than to use:

var method = typeof(Enumerable).GetMethods()
                               .Where(m => m.Name == "DefaultIfEmpty")
                               .Where(m => m.GetParameters().Length == 1)
                               .Single();

To call GetMethod, you'd have to have the exact correct parameter type, including the right generic type parameter for the parameter. Once you've got that once you could do it, but until then I think the above is all that's available :(