如何将多个foreach迭代更改为单个LINQ?

如果要将地址添加到另一个列表中,可以使用 SelectMany 和使用 AddRange :

emailAddresses.AddRange(notificationRequest.SelectMany(request =>
                  request.RequestXml.Descendants("SUBMITTERALIAS"))
                  .Select(email => email.Value));

如果您创建了一个完整的新列表,您可以这样简单地调用它:

emailAddresses = notificationRequest.SelectMany(request =>
                  request.RequestXml.Descendants("SUBMITTERALIAS"))
                  .Select(email => email.Value).ToList();

这应该可以做到:

var emailAddresses = notificationRequest.
    /// flatten the list of descendats list to email list
    SelectMany(request => request.RequestXml.Descendants("SUBMITTERALIAS")).
    /// select the value of the email element
    Select(email => email.Value).
    /// convert it to a List
    ToList();

request.RequestXml.Descendants("SUBMITTERALIAS").ToList().ForEach(x => emailAddresses.Add(x.Value));

您需要将查询扁平化,以便只返回一系列电子邮件地址:

var emailAddresses = 
    from request in notificationRequest
    from email in request.RequestXml.Descendants("SUBMITTERALIAS")
    select email.Value;

如果您确实需要它作为一个列表:

var emailAddressList = emailAddresses.ToList();

OO方法可能是创建一个 EmailAddresses() 中的方法 request :

public IEnumerable<string> EmailAddresses()
    => RequestXml.Descendants("SUBMITTERALIAS").Select(x => x.Value);

并更改您的查询以使用:

var emailAddresses = notificationRequest.SelectMany(x => x.EmailAddresses());