从 C# 到 VB.net 的 Linq

Question

我正在从 C# 尝试这个 LINQ 表达式，但它似乎不起作用

C#

var v = (from a in dc.ChatPrivateMessageMasters
                     join b in dc.ChatPrivateMessageDetails on a.EmailID equals b.MasterEmailID into cc
                     from c in cc
                     where (c.MasterEmailID.Equals(fromid) && c.ChatToEmailID.Equals(toid)) || (c.MasterEmailID.Equals(toid) && c.ChatToEmailID.Equals(fromid))
                     orderby c.ID descending
                     select new
                     {
                         UserName = a.UserName,
                         Message = c.Message,
                         ID = c.ID
                     }).Take(take).ToList();

VB

Dim v = (From a In dc.ChatPrivateMessageMasters _
Join b In dc.ChatPrivateMessageDetails On a.EmailID Equals b.MasterEmailID _
Into cc _
From c In cc Where (c.MasterEmailID.Equals(fromid) AndAlso c.ChatToEmailID.Equals(toid)) OrElse (c.MasterEmailID.Equals(toid) AndAlso c.ChatToEmailID.Equals(fromid)) _
Order By c.ID Descending _
Select New With { _
    .UserName = a.UserName, _
    .Message = c.Message, _
   .ID = c.ID _
}).Take(take).ToList()

我收到来自 'Into' 的错误消息：')' 预期

有什么想法吗？

// 更新我的数据库结构

Answer 1

对于初学者，您不需要组加入（join 子句的into 部分），考虑到您立即将其展平（例如，不要进行左外连接）。

您的 C# 查询可以是：

var query =
    (from m in dc.ChatPrivateMessageMasters
    join d in dc.ChatPrivateMessageDetails on m.EmailID equals d.MasterEmailID
    where (d.MasterEmailID == fromid && d.ChatToEmailID == toid)
       || (d.MasterEmailID == toid && d.ChatToEmailID == fromid)
    orderby d.ID descending
    select new
    {
        m.UserName,
        d.Message,
        d.ID
    }).Take(take).ToList();

VB.net 相当于：

Dim query =
    (From m In dc.ChatPrivateMessageMasters
    Join d In dc.ChatPrivateMessageDetails On m.EmailID Equals d.MasterEmailID
    Where (d.MasterEmailID = fromid AndAlso d.ChatToEmailID = toid)
    OrElse (d.MasterEmailID = toid AndAlso d.ChatToEmailID = fromid)
    Order By d.ID Descending
    Select m.UserName, d.Message, d.ID
    Take take).ToList