심플하게~

</table>

{

    public int iDisplayStart { get; set; }

    public int iDisplayLength { get; set; }

    public string sSearch { get; set; }

    public bool bEscapeRegex { get; set; }

    public int iColumns { get; set; }

    public int iSortingCols { get; set; }

    public int iSortCol_0 { get; set; }

    public string sSortDir_0 { get; set; }

    public int sEcho { get; set; }

    public bool bSortable_0 { get; set; }

    public bool bSearchable_0 { get; set; }

}

public class FormatedList

{

    public int sEcho { get; set; }

    public int iTotalRecords { get; set; }

    public int iTotalDisplayRecords { get; set; }

    public string[][] aaData { get; set; }

}

public static class QuerableExtensions

{

    public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string propertyName, bool asc)

    {

        var type = typeof(T);

        string methodName = asc ? "OrderBy" : "OrderByDescending";

        var property = type.GetProperty(propertyName);

        var parameter = Expression.Parameter(type, "p");

        var propertyAccess = Expression.MakeMemberAccess(parameter, property);

        var orderByExp = Expression.Lambda(propertyAccess, parameter);

        MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName, new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));

        return source.Provider.CreateQuery<T>(resultExp);

    }

}

public static class GridsUtils

{

    public delegate string[] GetStringDelegate<T>(T obj);

    public static string[][] GetStrings<T>(this IQueryable<T> source, GetStringDelegate<T> del)

    {

        string[][] retArray = new string[source.Count()][];

        int i = 0;

        foreach (var s in source)

        {

            retArray.SetValue(del(s), i);

            i++;

        }

        return retArray;

    }

}

{

    using (TestEntities Context = new TestEntities())

    {

        //data

        var query = Context.Parent.Include("Children").AsQueryable();

        int total = query.Count();

        //search whatever property you like

        if (!string.IsNullOrEmpty(gridParams.sSearch))

        {

            query = from x in query

                    where x.P_Name.Contains(gridParams.sSearch)

                    select x;

        }

        //sort

        if (gridParams.iSortingCols > 0)

        {

            var propertyName = "P_ID";

            switch (gridParams.iSortCol_0)

            {

                case 0: propertyName = "P_ID"; break;

                case 1: propertyName = "P_Name"; break;

            }

            query = query.OrderBy(propertyName, (gridParams.sSortDir_0 == "asc"));

        }

        //display

        int totaldisp = query.Count();

        if (gridParams.iDisplayLength > 0)

            query = query.Skip(gridParams.iDisplayStart).Take(gridParams.iDisplayLength);

        return Json(new FormatedList

        {

            sEcho = gridParams.sEcho,

            iTotalRecords = total,

            iTotalDisplayRecords = totaldisp,

            aaData = query.GetStrings(t => new string[]

            {

                t.P_ID.ToString(),

                t.P_Name,

                t.Children.Count.ToString()

            })

        });

    }

}

SELECT

[Project2].[P_ID] AS [P_ID],

[Project2].[P_Name] AS [P_Name],

[Project2].[C1] AS [C1],

[Project2].[C3] AS [C2],

[Project2].[C2] AS [C3],

[Project2].[C_ID] AS [C_ID],

[Project2].[C_Name] AS [C_Name],

[Project2].[P_ID1] AS [P_ID1]

FROM ( SELECT

       [Limit1].[P_ID] AS [P_ID],

       [Limit1].[P_Name] AS [P_Name],

       [Limit1].[C1] AS [C1],

       [Extent2].[C_ID] AS [C_ID],

       [Extent2].[C_Name] AS [C_Name],

       [Extent2].[P_ID] AS [P_ID1],

       CASE WHEN ([Extent2].[C_ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C2],

       CASE WHEN ([Extent2].[C_ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C3]

       FROM   (SELECT TOP (10) [Project1].[P_ID] AS [P_ID], [Project1].[P_Name] AS [P_Name], [Project1].[C1] AS [C1]

             FROM ( SELECT [Project1].[P_ID] AS [P_ID], [Project1].[P_Name] AS [P_Name], [Project1].[C1] AS [C1], row_number() OVER (ORDER BY [Project1].[P_ID] ASC) AS [row_number]

                    FROM ( SELECT

                           [Extent1].[P_ID] AS [P_ID],

                           [Extent1].[P_Name] AS [P_Name],

                           1 AS [C1]

                           FROM [dbo].[Parent] AS [Extent1]

                    )  AS [Project1]

             )  AS [Project1]

             WHERE [Project1].[row_number] > 0

             ORDER BY [Project1].[P_ID] ASC ) AS [Limit1]

       LEFT OUTER JOIN [dbo].[Children] AS [Extent2] ON [Limit1].[P_ID] = [Extent2].[P_ID]

)  AS [Project2]

ORDER BY [Project2].[P_ID] ASC, [Project2].[C3] ASC