System.Linq.Dynamic.ExpressionParser.ParseEnumerableMethods C# (CSharp) Method

		private Maybe<Expression> ParseEnumerableMethods(Expression instance, Type elementType, string methodName,
			Lazy<Expression[]> parseArgumentList)
		{
			ParameterExpression outerIt = _it;
			ParameterExpression innerIt = Expression.Parameter(elementType, "Param" + _paramCounter++);
			_it = innerIt;
			Expression[] args = parseArgumentList.Value;
			_it = outerIt;
			MethodBase signature;
			var typeArgs = new[] { elementType };
			if (methodName.EqualsIgnoreCase("Avg"))
			{
				methodName = "Average";
			}
			if (GetAppropriateMethodCount(typeof(IEnumerableAggregateSignatures), methodName, false, args, out signature) == 1)
			{
				if (signature.Name == "Min" || signature.Name == "Max")
				{
					typeArgs = new[] { elementType, args[0].Type };
				}
				args = args.Length == 0 ? new[] { instance } : new[] { instance, Expression.Lambda(args[0], innerIt) };
				return Expression.Call(typeof(Enumerable), signature.Name, typeArgs, args);
			}

			if (args.Length == 0)
				return Maybe.Nothing;

			var methodInfo = GetEnumerableMethod(methodName, new[] { elementType, args[0].Type });
			if (methodInfo == null)
				return Maybe.Nothing;

			var method = Expression.Call(methodInfo, instance, Expression.Lambda(args[0], innerIt));
			return method;
		}