Question

I have a sorting extension method with the following signature:

public static IEnumerable<T> CustomSort<T>(this IEnumerable<T> source, string sortProperties)

We wrote it a while back and it has been doing its thing. Now I am creating a custom control and the DataSource property is an IEnumerable (non-generic).
Is there any way to get the type of the objects in a non-generic IEnumerable?

I am sure the problem of “sort a custom control data source” has been solved a million times, but I just can’t seem to find a solution.

Answer 1

You could create an extension method that will return the correct type at runtime:

public static class LinqExtensions
{
    public static Type GetElementType(this IEnumerable source)
    {
        var enumerableType = source.GetType();
        if (enumerableType.IsArray)
        {
            return enumerableType.GetElementType();
        }
        if (enumerableType.IsGenericType)
        {
            return enumerableType.GetGenericArguments().First();
        }
        return null;
    }
}

Update: I’ve added the mechanism that I would use to perform the generic-specific IEnumerable<T> sorting on the non-generic IEnumerable

public static class SortingExtensions
{
    public static IEnumerable<T> CustomSort<T>(this IEnumerable<T> source, string sortProperties)
    {
        // sort here
    }

    public static IEnumerable CustomSort(this IEnumerable source, string sortProperties)
    {
        var elementType = source.GetElementType();
        var genericElementType = typeof (IEnumerable<>).MakeGenericType(elementType);

        var sortMethod = typeof (SortingExtensions).GetMethod(
            "CustomSort", 
            BindingFlags.Public | BindingFlags.Static,
            null, 
            new [] {genericElementType, typeof (string)},
            null);

        return (IEnumerable) sortMethod.Invoke(null, new object[] {source, sortProperties});
    }

}