Since Web API OData V5.9.0, it supports to bind the custom UriFunctions to CLR methods now, so user can add,modify or override the existing pre defined built-in functions.

Let’s see how to use this feature.

FunctionSignatureWithReturnType padrightStringEdmFunction =
                     new FunctionSignatureWithReturnType(
MethodInfo padRightStringMethodInfo = typeof(string).GetMethod("PadRight", new Type[] { typeof(int) });
const string padrightMethodName = "padright";
ODataUriFunctions.AddCustomUriFunction(padrightMethodName, padrightStringEdmFunction, padRightStringMethodInfo);

Then you can use filter function like $filter=padright(ProductName, 5) eq 'Abcd'.

Related Issue #612.