Question

鉴于此代码：

dgIPs.DataSource = 
    from act in Master.dc.Activities
    where act.Session.UID == Master.u.ID
    select new
    {
      Address = act.Session.IP.Address,
      Domain = act.Session.IP.Domain,
      FirstAccess = act.Session.IP.FirstAccess,
      LastAccess = act.Session.IP.LastAccess,
      IsSpider = act.Session.IP.isSpider,
      NumberProblems = act.Session.IP.NumProblems,
      NumberSessions = act.Session.IP.Sessions.Count()
    };

如何仅根据不同的地址拉出Distinct（）？也就是说，如果我只是添加Distinct（），它会将整行评估为不同，因此无法找到任何重复项。我想为每个act.Session.IP对象返回一行。

我已经找到了this answer，但似乎是另一种情况。此外，如果我只选择act.Session.IP，Distinct（）工作正常，但它有一个我希望避免检索的列，我宁愿不必通过手动绑定我的datagrid列来完成此操作。

Answer 1

dgIPs.DataSource = 
    from act in Master.dc.Activities
    where act.Session.UID == Master.u.ID
    group act by act.Session.IP.Address into g
    let ip = g.First().Session.IP
    select new
    {
      Address = ip.Address,
      Domain = ip.Domain,
      FirstAccess = ip.FirstAccess,
      LastAccess = ip.LastAccess,
      IsSpider = ip.isSpider,
      NumberProblems = ip.NumProblems,
      NumberSessions = ip.Sessions.Count()
    };

或者：

dgIPs.DataSource = 
    from act in Master.dc.Activities
    where act.Session.UID == Master.u.ID
    group act.Session.IP by act.Session.IP.Address into g
    let ip = g.First()
    select new
    {
      Address = ip.Address,
      Domain = ip.Domain,
      FirstAccess = ip.FirstAccess,
      LastAccess = ip.LastAccess,
      IsSpider = ip.isSpider,
      NumberProblems = ip.NumProblems,
      NumberSessions = ip.Sessions.Count()
    };

Answer 2

Enumerable.Distinct的一个重载接受IEqualityComparer实例。只需编写一个实现IEqualityComparer的类，它只比较两个Address属性。

不幸的是，您必须为您正在使用的匿名类命名。

Linq to SQL：匿名类型的DISTINCT

2 个答案: