linq 加入 or 条件

Question

我正在构建一个 linq 查询：

From G In Games _
            Where G.Field(Of Integer)("SystemID") = System _
            Join F In Files On _
            F.Field(Of String("Name") Equals G.Field(Of String)("PrimaryFilename") _
            Select New With {
                .gid = G.Field(Of Integer)("ID"),
                .ggamename = G.Field(Of String)("GameName")}

我希望连接发生在它等于一个值或另一个值的地方。像这样的东西（这自然是行不通的）：

From G In Games _
            Where G.Field(Of Integer)("SystemID") = System _
            Join F In Files On _
            F.Field(Of String("Name") Equals G.Field(Of String)("PrimaryFilename") OR G.Field(Of String)("SafeFilename") _
            Select New With {
                .gid = G.Field(Of Integer)("ID"),
                .ggamename = G.Field(Of String)("GameName")}

我该怎么办？

---

更新

以下有用的建议，但结果证明交叉连接太昂贵且速度太慢。我也试过下面的方法：

Dim query1 = _
            From G In Games _
            Where G.Field(Of Integer)("SystemID") = System _
            Join F In Files On _
            G.Field(Of String)("PrimaryFilename") Equals F.Field(Of String)("Name") _
            Select New With {
                .gid = G.Field(Of Integer)("ID"),
                .ggamename = G.Field(Of String)("GameName"),
                .gprimaryfilename = G.Field(Of String)("PrimaryFilename"),
                .gsafegamename = G.Field(Of String)("SafeGameName")}

dim  query2 = _
           From G In Games _
           Where G.Field(Of Integer)("SystemID") = System _
           Join F In Files On _
           G.Field(Of String)("SafeGameName") Equals F.Field(Of String)("Name") _
            Select New With {
            .gid = G.Field(Of Integer)("ID"),
            .ggamename = G.Field(Of String)("GameName"),
            .gprimaryfilename = G.Field(Of String)("PrimaryFilename"),
            .gsafegamename = G.Field(Of String)("SafeGameName")}

Dim query = query1.Union(query2)

但这产生了一些奇怪的结果（错误的匹配）——感觉有点超出我的深度。关于如何实现简单的“或”匹配还有其他建议吗？

Answer 1

Linq 仅支持 equi-joins。您可以尝试进行“交叉连接”并将条件放入您的 where 子句中：

From G In Games _
    Where G.Field(Of Integer)("SystemID") = System _
    From F In Files _
    Where (F.Field(Of String("Name") = G.Field(Of String)("PrimaryFilename")) _
       Or (F.Field(Of String("Name") = G.Field(Of String)("SafeFilename")) _
    Select New With {
        .gid = G.Field(Of Integer)("ID"),
        .ggamename = G.Field(Of String)("GameName")}