@Prog! - ASP.NET(C#) AJAX -

using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[ args)
        {
            using (Test1 db = new Test1(Settings1.Default.ConnectionString))
            {
                StreamWriter sw = new StreamWriter(@"d:\log.txt");
                sw.AutoFlush = true;
                TextWriter tw = TextWriter.Synchronized(sw);

                db.Log = tw;

                string[ ids = {"1", "3"};
                var rs = from t2 in db.Table_2
                          group t2 by t2.ID into g1
                         let i = g1.Key.ToString()
                         where ids.Contains(i)
                         select new { g1.Key, Total = g1.Sum(t2 => t2.Number) };

                foreach (var r in rs) Console.WriteLine(r);
            }

            Console.Read();
        }
    }
}

SELECT [t2].[ID] AS [Key], (
    SELECT SUM([t3].[Number])
    FROM [dbo].[Table_2] AS [t3]
    WHERE (([t2].[ID] IS NULL) AND ([t3].[ID] IS NULL)) OR (([t2].[ID] IS NOT NULL) AND ([t3].[ID] IS NOT NULL) AND ([t2].[ID] = [t3].[ID]))
    ) AS [Total]
FROM (
    SELECT [t1].[ID], CONVERT(NVarChar,[t1].[ID]) AS [value]
    FROM (
        SELECT [t0].[ID]
        FROM [dbo].[Table_2] AS [t0]
        GROUP BY [t0].[ID]
        ) AS [t1]
    ) AS [t2]
WHERE [t2].[value] IN (@p0, @p1)
-- @p0: Input NVarChar (Size = 1; Prec = 0; Scale = 0) [1]
-- @p1: Input NVarChar (Size = 1; Prec = 0; Scale = 0) [3]
-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.21022.8