Can Dynamic LINQ Ordering Be Applied to `IEnumerable` as Well as `IQueryable`?

Dynamic LINQ OrderBy on IEnumerable / IQueryable

In dynamic LINQ, you can use a SQL-like string (e.g., "OrderBy("Name, Age DESC")") to order the results. However, the examples available so far only work with IQueryable. This raises the question: is it possible to extend this functionality to IEnumerable?

Extending to IEnumerable

To achieve this, you can create wrapper methods that utilize AsQueryable. However, the code below serves as the core expression logic required:

public static IOrderedQueryable<T> OrderBy<T>(
    this IQueryable<T> source,
    string property)
{
    return ApplyOrder<T>(source, property, "OrderBy");
}

public static IOrderedQueryable<T> OrderByDescending<T>(
    this IQueryable<T> source,
    string property)
{
    return ApplyOrder<T>(source, property, "OrderByDescending");
}

public static IOrderedQueryable<T> ThenBy<T>(
    this IOrderedQueryable<T> source,
    string property)
{
    return ApplyOrder<T>(source, property, "ThenBy");
}

public static IOrderedQueryable<T> ThenByDescending<T>(
    this IOrderedQueryable<T> source,
    string property)
{
    return ApplyOrder<T>(source, property, "ThenByDescending");
}

static IOrderedQueryable<T> ApplyOrder<T>(
    IQueryable<T> 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 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<T>)result;
}

Incorporating Dynamic Functionality

For dynamic LINQ-to-Objects scenarios, you can leverage System.Dynamic for more flexibility.

using Microsoft.CSharp.RuntimeBinder;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

/// <summary>
/// OrderBy for dynamic IEnumerable operations
/// </summary>
public static IOrderedEnumerable<dynamic> OrderBy(
    this IEnumerable<dynamic> source,
    string property)
{
    return Enumerable.OrderBy<dynamic, object>(
        source,
        AccessorCache.GetAccessor(property),
        Comparer<object>.Default);
}

/// <summary>
/// OrderByDescending for dynamic IEnumerable operations
/// </summary>
public static IOrderedEnumerable<dynamic> OrderByDescending(
    this IEnumerable<dynamic> source,
    string property)
{
    return Enumerable.OrderByDescending<dynamic, object>(
        source,
        AccessorCache.GetAccessor(property),
        Comparer<object>.Default);
}

/// <summary>
/// ThenBy for dynamic IEnumerable operations
/// </summary>
public static IOrderedEnumerable<dynamic> ThenBy(
    this IOrderedEnumerable<dynamic> source,
    string property)
{
    return Enumerable.ThenBy<dynamic, object>(
        source,
        AccessorCache.GetAccessor(property),
        Comparer<object>.Default);
}

/// <summary>
/// ThenByDescending for dynamic IEnumerable operations
/// </summary>
public static IOrderedEnumerable<dynamic> ThenByDescending(
    this IOrderedEnumerable<dynamic> source,
    string property)
{
    return Enumerable.ThenByDescending<dynamic, object>(
        source,
        AccessorCache.GetAccessor(property),
        Comparer<object>.Default);
}

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