CODEWITHSUNDEEP
c#linqexpressionexpression-trees
user152949
user152949

Reputation:

How to access OrderBy clause from MethodCallExpression

I have a custom LINQ provider that processes a MethodCallExpression that has a OrderBy clause inside it. How can I get hold of the OrderBy clause so that I may process it?

Upvotes: 3

Views: 137

Answers (1)

user152949
user152949

Reputation:

I figured it out, here is how.

    public class QueryContext<T>
    {
        void Execute(MethodCallExpression dsQueryExpression)
        {
            var orderByFinder = new OrderByFinder();
            var orderByExpression = orderByFinder.GetOrderBy(dsQueryExpression);
            // .. Continue on processing the OrderBy expression
        }
    }

    internal class OrderByFinder : ExpressionVisitor
    {
        MethodCallExpression _orderByExpression;

        public MethodCallExpression GetOrderBy(Expression expression)
        {
            Visit(expression);
            return _orderByExpression;
        }

        protected override Expression VisitMethodCall(MethodCallExpression expression)
        {
            if (expression.Method.Name == "OrderBy") _orderByExpression = expression;

            Visit(expression.Arguments[0]);

            return expression;
        }
    }

Upvotes: 3

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