二、MVC3+EF单表增删改查

document 表为例 写入静态类 NorthwindDataProvider：

Controller可直接调用：如

 //获取document表全部数据
 NorthwindDataProvider.GetDocuments()

document 类：EF 映射

     public static class NorthwindDataProvider
     {
         const string NorthwindDataContextKey = "DXNorthwindDataContext";

         public static NWindEntities DB
         {
             get
             {
                 if (HttpContext.Current.Items[NorthwindDataContextKey] == null)
                     HttpContext.Current.Items[NorthwindDataContextKey] = new NWindEntities();
                 return (NWindEntities)HttpContext.Current.Items[NorthwindDataContextKey];
             }
         }
         /// <summary>
         /// 查询所有document表数据
         /// </summary>
         /// <returns></returns>
         public static IEnumerable GetDocuments()
         {
             return from document in DB.Documents select document;
         }
         /// <summary>
         /// 增加一条document数据
         /// </summary>
         /// <param name="doc">传入新数据</param>
         public static void AddDocument(Document doc)
         {
             DB.Documents.AddObject(doc);
             DB.SaveChanges();
         }
         /// <summary>
         /// 根据ID查询document数据
         /// </summary>
         /// <param name="id">传入主键</param>
         /// <returns></returns>
         public static Document GetDocumentById(int id)
         {
             var val = from document in DB.Documents where document.DocumentId == id select document;
             return val.First();
         }
         /// <summary>
         /// 修改一条document数据
         /// </summary>
         /// <param name="doc">传入修改后的数据</param>
         public static void UpdateDocument(Document doc)
         {
             Document oldDoc = DB.Documents.First(p => p.DocumentId == doc.DocumentId);
             oldDoc.DocumentCode = doc.DocumentCode == null ? oldDoc.DocumentCode : doc.DocumentCode;
             oldDoc.DocumentName = doc.DocumentName == null ? oldDoc.DocumentName : doc.DocumentName;
             oldDoc.DocumentMemo = doc.DocumentMemo == null ? oldDoc.DocumentMemo : doc.DocumentMemo;
             oldDoc.DocumentType = doc.DocumentType == null ? oldDoc.DocumentType : doc.DocumentType;
             oldDoc.DocumentDate = doc.DocumentDate == null ? oldDoc.DocumentDate : doc.DocumentDate;
             DB.SaveChanges();
         }
         /// <summary>
         /// 删除一条document数据
         /// </summary>
         /// <param name="id">被删除数据的主键</param>
         public static void deleteDocument(int id)
         {
             var obj = DB.Documents.Where(c => c.DocumentId == id).First();
             DB.DeleteObject(obj);
             DB.SaveChanges();
         }
     }