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();
        }
    }