Dynamic LINQ OrderBy

Just stumbled into this oldie...

To do this without the dynamic LINQ library, you just need the code as below. This covers most common scenarios including nested properties.

To get it working with IEnumerable you could add some wrapper methods that go via AsQueryable - but the code below is the core Expression logic needed.

    public static IOrderedQueryable OrderBy(this IQueryable source, string property)
    {
        return ApplyOrder(source, property, "OrderBy");
    }
    public static IOrderedQueryable OrderByDescending(this IQueryable source, string property)
    {
        return ApplyOrder(source, property, "OrderByDescending");
    }
    public static IOrderedQueryable ThenBy(this IOrderedQueryable source, string property)
    {
        return ApplyOrder(source, property, "ThenBy");
    }
    public static IOrderedQueryable ThenByDescending(this IOrderedQueryable source, string property)
    {
        return ApplyOrder(source, property, "ThenByDescending");
    }
    static IOrderedQueryable ApplyOrder(IQueryable source, string property, string methodName) {
        string[] props = property.Split('.');
        Type type = typeof(T);
        ParameterExpression arg = Expression.Parameter(type, "x");
        Expression expr = arg;
        foreach(string prop in props) {
            // use reflection (not ComponentModel) to mirror LINQ
            PropertyInfo pi = type.GetProperty(prop);
            expr = Expression.Property(expr, pi);
            type = pi.PropertyType;
        }
        Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
        LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);

        object result = 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[] {source, lambda});
        return (IOrderedQueryable)result;
   }