C# Linq查询-实体框架（连接两个表）

我对LINQ查询有问题。在towar桌上我想要Kategorie，Nazwa

sql中的示例：从Towar.Id_kat=Kategorie.Id_kat上的Towar内部连接Kategorie中选择Kategorie.Nazwa

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这是我的问题。其中p=>category==null | | p.Id_kat==category我需要类别的名称，但我有编号。我需要这个p.Id_kat=SELECT Kategorie.Nazwa从Towar内部使用EntityFramework DbContext在Towar.Id_kat=Kategorie.Id_kat I上连接Kategorie

SomeView viewModel = new SomeView
                {
                    Towar = repository.Towar
                    .Where(p => category == null || p.Id_kat == category)
                    .OrderBy(p => p.Id_tow)
                    .Skip((page - 1) * PageSize)
                    .Take(PageSize),

                    Kategorie = re.Kategorie
                    .OrderBy(p => p.Id_kat),

                    PagingInfo = new PagingInfo
                                        {
                                       CurrentPage = page,
                                       ItemsPerPage = PageSize,
                                       TotalItems = repository.Towar.Count()

                                        },
                    CurrentCategory = category

                                   };
                return View(viewModel);
            }

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如果在Towar和Kategories之间设置外键，则不必进行连接。您可以使用POCO类引用Kategory类和powerofentity框架。下面是一个关于测试的示例：

请注意Towar类如何具有Kategory类的属性

[ Subject( "Inner join example using entity framework") ]
public class When_getting_towar_by_kategory_and_there_are_2_kategories
{
    Establish context = () =>
                        {
                            myContext = new MyContext();
                            Database.SetInitializer(new CreateDatabaseIfNotExists<MyContext>());
                            var first = new Kategory { Nazwa = "First" };
                            myContext.Kategories.Add(first);
                            var second = new Kategory { Nazwa = "Second" };
                            myContext.Kategories.Add(second);
                            myContext.Towars.Add(new Towar { Cena = "found", Kategory = first });
                            myContext.Towars.Add(new Towar { Cena = "notFound", Kategory = second });
                            myContext.SaveChanges();
                            SUT = new Controller(myContext);
                        };


    private Because of = () => { result = SUT.GetTowarByKategory("First"); };

    private It should_return_list_filtered_by_kategory = () => { result.Select(x => x.Cena).SequenceEqual(new[] { "found" }).Should().BeTrue(); };
    private static Controller SUT;
    private static IEnumerable<Towar> result;
    private static MyContext myContext;
}


public class Controller
{
    private readonly MyContext context;

    public Controller(MyContext context)
    {
        this.context = context;
    }
    public IEnumerable<Towar> GetTowarByKategory(string category)
    {
        var res = from t in context.Towars
                    where t.Kategory.Nazwa == category
                    select t;

        return res;
    }
}

public class Kategory
{
    [Key] 
    public int Id_kat { get; set; }
    public string Nazwa { get; set; }
}

public class Towar
{
    [Key]
    public int Id_tow { get; set; }
    public Kategory Kategory { get; set; }
    public string Cena { get; set; }
}

public class MyContext : DbContext
{
    public DbSet<Kategory> Kategories { get; set; }
    public DbSet<Towar> Towars { get; set; }
}

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您的类别变量是存储在Kategorie.Nazwa中的值吗？Kategorie.Nazwa-nvarchar50p.Id_kat=从Towar.Id_kat=Kategorie.Id_kat上的Towar内部连接Kategorie中选择Kategorie.Nazwa，这是什么意思？现在p.Id_kat是相等的数字，但我需要这样的东西->从Towar内部选择Kategorie.Nazwa在Towar上加入Kategorie.Id_kat=Kategorie.Id_kat我需要类别名称，但现在我有了类别Id号