LINQ query in C# using string on the fly to ORDER data

I have a function with two strings. Can't figure out how to incorporate those two strings into a LINQ query.

Here is my function:

private void DataBind_GridView_Search(string OptionalArgsSortExpression = "", string OptionalArgsSortDirection = "")
{
List<mainSearchDataModel> Query = GetData();
if (Query != null)
{


    /* Problem ... */
    Query = from x in Query
            orderby OptionalArgsSortExpression.ToString() OptionalArgsSortDirection.ToString()
            select x;
    /* Problem ... */


    GridView_Search.DataSource = Query;
    GridView_Search.DataBind();
}

Any comments would be highly appreciated.

This is the error I get. Also I am not using DLINQ.

'System.Linq.Enumerable.OrderBy(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

UPDATE:

Is there a way to ORDER a List or IEnumerable either one. It seems everything I try does not work.

There is a way to convert it to DataView but I run into trouble there as well and would rather not go that way.