Question

为什么where条件未在以下代码中应用？当我搜索时，结果不会被过滤。当我调试时，searchString确实有一个值，执行正在通过_data.Where子句，但它没有返回过滤结果。

我在这里做错了什么？

IQueryable<UserViewModel> _data = (
    from a in context.aspnet_Users
    join b in context.aspnet_Membership on a.UserId equals b.UserId
    where b.IsApproved == true
    select new UserViewModel
    {                                 
        UserId = a.UserId,
        UserName = a.UserName,
        FirstName = a.FirstName,
        LastName = a.LastName,
        EmailAddress = b.Email                                 
    })
    .OrderBy(a => a.FirstName)
    .ThenBy(b => b.LastName);

if (!String.IsNullOrEmpty(searchString))
{                  
   _data = _data
        .Where(x => x.FirstName.Contains(searchString))
        .Where(y => y.UserName.Contains(searchString))
        .Where(y => y.LastName.Contains(searchString))
        .Where(y => y.EmailAddress.Contains(searchString));
}

Answer 1

编写第二个查询的方式检查所有过滤字段以搜索字符串开头的记录，即对于FirstName 和 LastName 和 UserName 和电子邮件都以相同的字符串开头。

我认为你想要的是一个查询，检查这些字段是否以搜索字符串开头，例如：

_data = _data.Where(x => x.FirstName.Contains(searchString) || x.UserName.Contains(searchString) || x.LastName.Contains(searchString) || x.EmailAddress.Contains(searchString));

Answer 2

我怀疑这比你期望的更多“过滤”：

_data = _data.Where(x => x.FirstName.Contains(searchString))
             .Where(y => y.UserName.Contains(searchString))
             .Where(y => y.LastName.Contains(searchString))
             .Where(y => y.EmailAddress.Contains(searchString));

这要求这些字段的所有四个中都存在searchString。因此，如果您搜索“David”，那么它将无法找到我的记录，因为我的LastName不包含该字符串。

也许您想使用逻辑或而不是逻辑和？像这样：

_data = _data.Where(x => x.FirstName.Contains(searchString) ||
                         x.UserName.Contains(searchString) ||
                         x.LastName.Contains(searchString) ||
                         x.EmailAddress.Contains(searchString));

LINQ to SQL - 过滤了WHERE子句

2 个答案: