private static IQueryable <T> ApplyOrderBy <T>(IQueryable <T> collection, OrderByInfo orderByInfo)
{
Type type = typeof(T);
ParameterExpression arg = Expression.Parameter(type, "x");
Expression expr = arg;
string prop = orderByInfo.PropertyName;
// use reflection (not ComponentModel) to mirror LINQ
PropertyInfo pi = OrmHelper.GetPropertyInfo <T>(prop);
expr = Expression.Property(expr, pi);
type = pi.PropertyType;
Type delegateType = typeof(Func <,>).MakeGenericType(typeof(T), type);
LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
string methodName = String.Empty;
if (!orderByInfo.Initial && collection is IOrderedQueryable <T> )
{
methodName = orderByInfo.Direction == SortDirection.Ascending ? "ThenBy" : "ThenByDescending";
}
else
{
methodName = orderByInfo.Direction == SortDirection.Ascending ? "OrderBy" : "OrderByDescending";
}
//TODO: apply caching to the generic methodsinfos?
return((IOrderedQueryable <T>) typeof(Queryable).GetMethods().Single(
method => method.Name == methodName &&
method.IsGenericMethodDefinition &&
method.GetGenericArguments().Length == 2 &&
method.GetParameters().Length == 2)
.MakeGenericMethod(typeof(T), type)
.Invoke(null, new object[] { collection, lambda }));
}
