1. linq查詢數據

WebTestDBEntities db = new WebTestDBEntities();

1.1 linq查詢所有列數據

     var userInfoList = from u in db.UserInfo
                               where u.ID == 10
                               select u;

1.2 linq查詢部分列數據

   var userInfoList = from u in db.UserInfo
                               
 
where u.ID >= 1
                               select new { Name = u.UserName, Pwd = u.UserPass };

            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.Name + ":" + userInfo.Pwd + "<br/>");
            }

2. lambda查詢數據

2.1 lambda查詢所有列數據

 var userInfoList = db.UserInfo.Where<UserInfo>(u => u.ID > 0);
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.UserName + ":" + userInfo.UserPass + "<br/>");
            }

2.2 lambda查詢部分列數據

    var userInfoList = db.UserInfo.Where<UserInfo>(u => u.ID > 0
 
).Select(a => new { Name = a.UserName, Pwd = a.UserPass });
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.Name + ":" + userInfo.Pwd + "<br/>");
            }

3. 排序

var userInfoList = db.UserInfo.Where<UserInfo>(c => true).OrderBy<UserInfo, int>(u => u.ID).Select(u => new { Name = u.UserName,Email=u.Email });//升序排序

            var userInfoList = db.UserInfo.Where<UserInfo>(c => true).OrderByDescending<UserInfo, int>(u => u.ID).Select(u => new { Name = u.UserName, Email = u.Email });//降序排序

            var userInfoList = (from u in db.UserInfo
                                select u).OrderByDescending<UserInfo, int>(c => c.ID).Select(u => new { Name = u.UserName, Email = u.Email });

4. 分頁查詢示例：

   int pageIndex = 2;
            int pageSize = 2;
            var userInfoList = db.UserInfo.Where<UserInfo>(c => true).OrderBy<UserInfo, int>(u => u.ID).Skip<UserInfo>((pageIndex - 1) * pageSize).Take<UserInfo>(pageSize);
            foreach (var userInfo in userInfoList)
            {
                Response.Write(userInfo.UserName + "<br/>");
            }

5、擴展方法

語法要求：

• 擴展方法所在的類必須是static
• 擴展方法必須是一個靜態方法
• 擴展方法的第一個參數，必須用this關鍵字修飾，而且類型是所擴展的類型

•   public static string ShowMsg(this string ext, string msg)
          {
              return string.Format("<span style=‘color:red‘>{0}</span>", msg);
          }

 string tempStr = string.Empty;
            string resultStr = tempStr.ShowMsg("擴展方法示例");
            Response.Write(resultStr);

EF下lambda與linq查詢&&擴展方法