Createing Expression<Func<IQueryable<T>, IOrderedQueryable<T>>>?

Question

I wanna create an Expression<Func<IQueryable<T>, IOrderedQueryable<T>>>, I have the following codes :

Expression selector = q => q.RegistrationDate

MethodInfo orderByMethodInfo = typeof(Queryable).GetMethods().First(method => method.Name == "OrderBy" && method.GetParameters().Count() == 2).MakeGenericMethod(argumentTypes);
MethodInfo orderByDescMethodInfo = typeof(Queryable).GetMethods().First(method => method.Name == "OrderByDescending" && method.GetParameters().Count() == 2).MakeGenericMethod(argumentTypes);

I'm gonna create c => c.OrderBy(q => q.RegistrationDate) or c => c.OrderByDescending(q => q.RegistrationDate) or generally something like c => c.OrderByDescending(q => q.RegistrationDate).ThenBy(q=>q.Name) from above codes.

Could you please guide how I can do it?

Answer 1

var paramExpr = Expression.Parameter(typeof(IQueryable<T>))
var orderByExpr = Expression.Call(orderByMethodInfo, paramExpr, selector);
var expr = Expression.Lambda<Func<IQueryable<T>, IOrderedQueryable<T>>>(orderByExpr, paramExpr);

Where T is the type with the RegistrationDate property in your selector expression.

You can get the queryable type from the argument type using MakeGenericType:

Type argType = typeof(DateTime);
Type queryableType = typeof(IQueryable<>).MakeGenericType(argType);