c# - 如何将查询语法转换为方法语法

Question

我正在四处游荡，试图了解 LINQ 的来龙去脉。我想将以下查询(工作正常)从查询语法转换为方法语法，但我似乎无法正确处理。谁能告诉我实现该目标的正确方法？

var logQuery = from entry in xDoc.Descendants("logentry")
               where (entry.Element("author").Value.ToLower().Contains(matchText) ||
                      entry.Element("msg").Value.ToLower().Contains(matchText) ||
                      entry.Element("paths").Value.ToLower().Contains(matchText) ||
                      entry.Element("revision").Value.ToLower().Contains(matchText))
               select new
               {
                   Revision = entry.Attribute("revision").Value,
                   Author = entry.Element("author").Value,
                   CR = LogFormatter.FormatCR(entry.Element("msg").Value),
                   Date = LogFormatter.FormatDate(entry.Element("date").Value),
                   Message = LogFormatter.FormatComment(entry.Element("msg").Value),
                   ET = LogFormatter.FormatET(entry.Element("msg").Value),
                   MergeFrom = LogFormatter.FormatMergeFrom(entry.Element("msg").Value),
                   MergeTo = LogFormatter.FormatMergeTo(entry.Element("msg").Value)
               };

Answer 1

其实很简单；

from entry in A
where B

翻译(字面意思)为:

A.Where(entry=>B)

和:

select C

直接翻译为(以“entry”为上下文):

.Select(entry=>C)

(除非它是 entry=>entry，编译器会在非平凡情况下忽略它)

所以只需注入(inject)这些就可以了:

var logQuery = xDoc.Descendants("logentry")
               .Where(entry=>
                          entry.Element("author").Value.ToLower().Contains(matchText) ||
                          entry.Element("msg").Value.ToLower().Contains(matchText) ||
                          entry.Element("paths").Value.ToLower().Contains(matchText) ||
                          entry.Element("revision").Value.ToLower().Contains(matchText))
                .Select(entry=>new
                   {
                       Revision = entry.Attribute("revision").Value,
                       Author = entry.Element("author").Value,
                       CR = LogFormatter.FormatCR(entry.Element("msg").Value),
                       Date = LogFormatter.FormatDate(entry.Element("date").Value),
                       Message = LogFormatter.FormatComment(entry.Element("msg").Value),
                       ET = LogFormatter.FormatET(entry.Element("msg").Value),
                       MergeFrom = LogFormatter.FormatMergeFrom(entry.Element("msg").Value),
                       MergeTo = LogFormatter.FormatMergeTo(entry.Element("msg").Value)
                   });