linq喜欢空字符串

Question

var list = (from i in _dataContext.aspnet_Users.Include("aspnet_Membership")  where i.UserName.Contains(userName)  select i ).ToList();

如果userName=""则没有任何回报。如果空字符串然后返回所有记录，我怎么能这样做？

Answer 1

执行：

  var list = 
      (from i in _dataContext.aspnet_Users.Include("aspnet_Membership") 
        where string.IsNullOrEmpty(userName)
               || i.UserName.Contains(userName)  
       select i ).ToList();

Answer 2

有趣的事实：System.Data.Linq.SqlClient命名空间包含一些非常有用的辅助方法。

你可以使用SqlMethods.Like函数，如果传递一个空字符串，它将返回所有结果。

例如：

 (from i in _dataContext.aspnet_Users.Include("aspnet_Membership") 
  where SqlMethods.Like(i.UserName, "%" + userName + "%")
  select i).ToList();