以下LINQ查询有什么问题？

I have been trying to dive into more advanced features of C# like LINQ and Lambda expressions, so I am a complete beginner when it comes to LINQ ans Lambda expressions.
My problem is that I have a list of paths of files contained on my computer and want to sort them based on the "last access time". To do this I wrote the following

我一直试图深入研究C＃的更高级功能，如LINQ和Lambda表达式，所以当涉及到LINQ和Lambda表达式时，我是一个完全的初学者。我的问题是我有一个包含在我的计算机上的文件路径列表，并希望根据“上次访问时间”对它们进行排序。为此，我写了以下内容

TempList = FilesList.OrderByDescending((FileInfo Files,string  n) => { Files = new    FileInfo(n) ; 
                                                                                Files.LastAccessTime ; }  ) ;

FilesList contains the paths of files in various orders. FilesList is of type list<string> and TempList is of type IEnumerable<string>.

FilesList包含各种顺序的文件路径。 FilesList的类型为list ，TempList的类型为IEnumerable 。

To this query compiler is generating the following error:

对此查询编译器生成以下错误：

The type arguments for method 'System.Linq.Enumerable.OrderByDescending<TSource,TKey>(System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,TKey>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

无法从用法中推断出方法'System.Linq.Enumerable.OrderByDescending （System.Collections.Generic.IEnumerable ，System.Func ）'的类型参数。尝试显式指定类型参数。，tkey> ，tkey>

Can someone please point out what is wrong with my query. I am unable to understand from the error message.

有人可以指出我的查询有什么问题。我无法从错误消息中理解。

2 个解决方案

#1

First of all, there is no way to get FileInfo parameter when FilesList is List<string>. You just get string. Furthermore, you don't return anything from your lambda. And you can't reassign lambda parameters either.

首先，当FilesList为List 时，无法获取FileInfo参数。你得到字符串。此外，你不会从你的lambda返回任何东西。而且你也不能重新分配lambda参数。

TempList = FilesList.OrderByDescending(n => new FileInfo(n).LastAccessTime);

Or, if you want to use {} within your lambda to make it multi-line lambda, you have to return something somewhere in the code (most likely as the last statement):

或者，如果你想在你的lambda中使用{}来使它成为多行lambda，你必须在代码中的某处返回一些东西（最有可能是最后一个语句）：

TempList = FilesList.OrderByDescending(n => { var file = new FileInfo(n); return file.LastAccessTime });

#2

Try this instead (assuming your list of "files" is actually a list of fully-qualified file names):

试试这个（假设你的“文件”列表实际上是一个完全限定的文件名列表）：

TempList = FilesList.OrderByDescending(n => new FileInfo(n).LastAccessTime).ToList();

I can't promise the syntax is completely correct as I don't have a list of files to run it on. Also, there may be more efficient methods than instantiating a FileInfo object for each file.

我不能保证语法是完全正确的，因为我没有要运行它的文件列表。此外，可能有比为每个文件实例化FileInfo对象更有效的方法。

#1