LINQ 개발 환경 설정 
; https://www.sysnet.pe.kr/2/0/458

using System;
using System.Collections.Generic;
using System.Text;
using System.Query;
using System.Xml.XLinq;
using System.Data.DLinq;

Error	1	'System.Collections.Generic.List<TestApp.Contact>' does not contain a definition for 'Where'
C:\temp\Program.cs

C:\Windows\Microsoft.NET\Framework\v3.5.11209\.NET 3.5
	System.Core.dll
	System.Data.Entity.dll
	System.Data.Linq.dll
	System.Xml.Linq.dll

using System.Data.DLinq;
using System.Xml.XLinq;
using System.Xml.Linq;
using System.Linq;
using System.Linq.Expressions;