protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.HasArgImplementing(typeof(IQueryable)))
{
var newArgs = node.Arguments.Select(a => StripQuotes(base.Visit(a))).ToArray();
// TODO: This is an imperfect shortcut to find an Enumerable
// method that corresponds to the given Queryable method.
// Should work for most (if not all) LINQ operators, though,
// which is primarily what we are after. To do this
// "correctly", i.e., the same as what the compiler does,
// we'd need to effectively reproduce extension method lookup,
// generic overload resolution, etc. This is not trivial.
var newMethod = typeof(Enumerable).GetMethods().FirstOrDefault(
m => m.Name == node.Method.Name &&
newArgs.Length == m.GetParameters().Length &&
newArgs.Zip(m.GetParameters().Select(p => p.ParameterType),
(arg, type) => arg.Type.Implements(type.GetGenericTypeDefinition())).All(b => b == true));
if (newMethod == null)
{
throw new Exception("Couldn't find IEnumerable<> replacement for method " + node.Method.Name);
}
if (newMethod.IsGenericMethod)
{
newMethod = newMethod.MakeGenericMethod(node.Method.GetGenericArguments().Select(
t => t.Implements(typeof(IQueryable <>)) ?
typeof(IEnumerable <>).MakeGenericType(t.GetGenericArguments()[0])
: t).ToArray());
}
return(Expression.Call(newMethod, newArgs));
}
else
{
return(base.VisitMethodCall(node));
}
}
