Dynamic LINQ help for sorting problem

Question

I have a simple IEnumerable collection of Order objects. I want to write a generic sort function that accepts the collection and a sortkey that corresponds to a property on an Order object. I don't want to hardcode the sort instructions for every property. How can I build a dynamic LINQ string that automatically generates the LINQ for me? Here is my SortOrders() function in its current state:

public IEnumerable<Order> SortOrders(IEnumerable<Order> orders, string sortKey)
        {
            // Sort order records
            try
            {
                IEnumerable<Order> sortedOrders = new List<Order>();

                // Extract sort key and direction from combined sortKey input
                string _sortKey = this.SortKey.Replace(" ASC", "").Replace(" DESC", "");
                bool sortASC = this.SortKey.EndsWith(" ASC");

                switch (_sortKey)
                {
                    case "CustomerID":
                        sortedOrders = (sortASC) ? orders.OrderBy(o => o.CustomerID) : orders.OrderByDescending(o => o.CustomerID);
                        break;
                    case "CustomerAddress":
                        sortedOrders = (sortASC) ? orders.OrderBy(o => o.CustomerAddress) : orders.OrderByDescending(o => o.CustomerAddress);
                        break;
                    case "CustomerCity":
                        sortedOrders = (sortASC) ? orders.OrderBy(o => o.CustomerCity) : orders.OrderByDescending(o => o.CustomerCity);
                        break;
                    default:
                        sortedOrders = orders;
                        break;
                }
                return sortedOrders;
            }
            catch
            {
                return orders; // return original orders list in the event of errors
            }
        }

I am looking to replace all of the case sections like this:

case "CustomerID":
                        sortedOrders = (sortASC) ? orders.OrderBy(o => o.CustomerID) : orders.OrderByDescending(o => o.CustomerID);

with a single directive like this:

sortedOrders = (sortASC) ? orders.OrderBy(o => o.PropertyName) : orders.OrderByDescending(o => o.PropertyName);

Answer 1

You can pass the expression you want to sort in as a Lamba (this is simplified/pseudocode)

SortOrders(IEnumerable<Order> orders, Func<Order, string> func)
{
    sortedOrders = orders.OrderBy(func) 
    ....                
}


// call:
SortOrders(orders,  o => o.CustomerID);

Answer 2

You can use Dynamic LINQ and there's no need for the extension method. Just use the extension in the DynamicQueryable class and specify both the key and direction as a string.

var sorted = orders.OrderBy( "CustomerID desc" );