C# 如何将带有join的linq表达式转换为lambda表达式？

我有以下的表达：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

我想换成lambda。我试过：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

_callPairs = _requests.Where(req => (_responses.Where(res => res.RequestId == 
    req.RequestId)).Where(!string.IsNullOrEmpty(req.RequestId)).ToList();

不幸的是，这没有编译

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

有人能给我解释一下如何将带有连接的linq表达式转换为lambda表达式吗？

只需使用以下方法：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

只需使用以下方法：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

---

这取决于联接的类型。这里有一个内部联接（可以通过缺少

into

子句来判断），因此相应的扩展方法语法使用：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

---

对于组联接（

join…on…into…

），您将改为使用。

这取决于联接的类型。这里有一个内部联接（可以通过缺少

into

子句来判断），因此相应的扩展方法语法使用：

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();

对于组联接（

join…on…to…

），您将使用

_callPairs = (from req in _requests
                      join resp in _responses
                          on req.RequestId equals resp.RequestId
                          where !string.IsNullOrEmpty(req.RequestId)
                      select new CallPair(req, resp)).ToList();