相关疑难解决方法(0)

我从XML中设置了以下项目:

id           category

5            1
5            3
5            4
5            3
5            3

我需要这些项目的清单:

5            1
5            3
5            4

如何在LINQ中区分Category AND Id？

class Program
{
    static void Main(string[] args)
    {
        List<Book> books = new List<Book> 
        {
            new Book
            {
                Name="C# in Depth",
                Authors = new List<Author>
                {
                    new Author 
                    {
                        FirstName = "Jon", LastName="Skeet"
                    },
                     new Author 
                    {
                        FirstName = "Jon", LastName="Skeet"
                    },                       
                }
            },
            new Book
            {
                Name="LINQ in Action",
                Authors = new List<Author>
                {
                    new Author 
                    {
                        FirstName = "Fabrice", LastName="Marguerie"
                    },
                     new Author 
                    {
                        FirstName = "Steve", LastName="Eichert"
                    },
                     new Author 
                    {
                        FirstName = "Jim", LastName="Wooley"
                    },
                }
            }, …

所以,说我有以下内容:

public class Element
{
  public int ID;
  public int Type;
  public Properties prorerty;
  ...
}

public class Properties
{
  public int Id;
  public string Property;
  ...
}

List Elements = new List();