PagedListHelpers.cs

using System;
using System.Collections.Generic;
using System.Linq;
using PagedList;

public class DataTablesSearch
{
	public string Value { get; set; }
	public bool Regex { get; set; }
}

public class DataTablesOrder
{
	public int Column { get; set; }
	public string Dir { get; set; }
}

public class DataTablesColumn
{
	public string Data { get; set; }
	public string Name { get; set; }
	public bool Searchable { get; set; }
	public bool Orderable { get; set; }
	public DataTablesSearch Search { get; set; }
}

public class DataTablesParam
{
	public int Draw { get; set; }
	public int Start { get; set; }
	public int Length { get; set; }
	public DataTablesSearch Search { get; set; }
	public List<DataTablesOrder> Order { get; set; }
	public DataTablesColumn[] Columns { get; set; }

	public int PageNumber
	{
		get
		{
			if (Length == 0)
			{
				return 1;
			}
			return Start/Length + 1;
		}
	}

	public int PageSize
	{
		get { return Length; }
	}

	public PagingCriteria ToPagingCriteria()
	{
		return new PagingCriteria()
		{
			Page = PageNumber,
			PageSize = PageSize,
			SortFields = Order.Select(x => new SortField(Columns[x.Column].Name ?? Columns[x.Column].Data, x.Dir)).ToArray()
		};
	}
}

public static class DataTablesExtensions
{
	public static JsonResult ToDataTableResult<T>(this IPagedList<T> results, int draw)
	{
		return new JsonResult()
		{
			Data = new
			{
				recordsTotal = results.TotalItemCount,
				recordsFiltered = results.TotalItemCount,
				draw,
				data = results.Cast<object>().ToArray()
			}
		};
	}
}

public static class PagedListExtensions
{
	/// <summary>
	/// Map the items in a paged list
	/// </summary>
	public static IPagedList<TResult> Select<TSource, TResult>(this IPagedList<TSource> source,
		Func<TSource, TResult> selector)
	{
		if (source == null)
		{
			throw new ArgumentNullException("source");
		}
		if (selector == null)
		{
			throw new ArgumentNullException("selector");
		}
		return new StaticPagedList<TResult>(source.AsEnumerable().Select(selector), source.PageNumber, source.PageSize,
			source.TotalItemCount);
	}

	/// <summary>
	/// This function assumes we can trust the column names coming from the client. It would be more secure to reference a separate copy of
	/// sortable column names on the server side, but there is a maintenance overhead as well.
	/// </summary>
	public static IPagedList<TSource> TrustedSortToPagedList<TSource>(this IEnumerable<TSource> source, PagingCriteria pagingCriteria)
	{
		if (source == null)
		{
			throw new ArgumentNullException("source");
		}
		return source.AsQueryable().TrustedSortToPagedList(pagingCriteria);
	}

	/// <summary>
	/// This function assumes we can trust the column names coming from the client. It would be more secure to reference a separate copy of
	/// sortable column names on the server side, but there is a maintenance overhead as well.
	/// </summary>
	public static IPagedList<TSource> TrustedSortToPagedList<TSource>(this IQueryable<TSource> source, PagingCriteria pagingCriteria)
	{
		if (source == null)
		{
			throw new ArgumentNullException("source");
		}
		if (pagingCriteria == null)
		{
			throw new ArgumentNullException("pagingCriteria");
		}
		var sortedSource = source.SortBySortField(pagingCriteria.SortFields.ToArray());
		if (pagingCriteria.IsNotPaged)
		{
			var count = sortedSource.Count();
			var pageSize = count == 0 ? 1 : count;
			return sortedSource.ToPagedList(1, pageSize);
		}
		return sortedSource.ToPagedList(pagingCriteria.Page, pagingCriteria.PageSize);
	}
}