LINQ: "berisi" dan permintaan Lambda

Saya telah a List<BuildingStatus>disebut buildingStatus. Saya ingin memeriksa apakah ini berisi status yang kode arang (dikembalikan oleh GetCharCode()) sama dengan beberapa variabel v.Status,.

Apakah ada cara untuk melakukan ini, di sepanjang baris kode (non-kompilasi) di bawah ini?

buildingStatus.Contains(item => item.GetCharValue() == v.Status)

Gunakan Any()alih-alih Contains():

buildingStatus.Any(item => item.GetCharValue() == v.Status)

Metode ekstensi Linq Apa saja bisa bekerja untuk Anda ...

buildingStatus.Any(item => item.GetCharValue() == v.Status)

Inilah cara yang dapat Anda gunakan Containsuntuk mencapai apa yang Anda inginkan:

buildingStatus.Select(item => item.GetCharValue()).Contains(v.Status) ini akan mengembalikan nilai Boolean.

Saya tidak yakin persis apa yang Anda cari, tetapi program ini:

    public class Building
    {
        public enum StatusType
        {
            open,
            closed,
            weird,
        };

        public string Name { get; set; }
        public StatusType Status { get; set; }
    }

    public static List <Building> buildingList = new List<Building> ()
    {
        new Building () { Name = "one", Status = Building.StatusType.open },
        new Building () { Name = "two", Status = Building.StatusType.closed },
        new Building () { Name = "three", Status = Building.StatusType.weird },

        new Building () { Name = "four", Status = Building.StatusType.open },
        new Building () { Name = "five", Status = Building.StatusType.closed },
        new Building () { Name = "six", Status = Building.StatusType.weird },
    };

    static void Main (string [] args)
    {
        var statusList = new List<Building.StatusType> () { Building.StatusType.open, Building.StatusType.closed };

        var q = from building in buildingList
                where statusList.Contains (building.Status)
                select building;

        foreach ( var b in q )
            Console.WriteLine ("{0}: {1}", b.Name, b.Status);
    }

menghasilkan output yang diharapkan:

one: open
two: closed
four: open
five: closed

Program ini membandingkan representasi string dari enum dan menghasilkan output yang sama:

    public class Building
    {
        public enum StatusType
        {
            open,
            closed,
            weird,
        };

        public string Name { get; set; }
        public string Status { get; set; }
    }

    public static List <Building> buildingList = new List<Building> ()
    {
        new Building () { Name = "one", Status = "open" },
        new Building () { Name = "two", Status = "closed" },
        new Building () { Name = "three", Status = "weird" },

        new Building () { Name = "four", Status = "open" },
        new Building () { Name = "five", Status = "closed" },
        new Building () { Name = "six", Status = "weird" },
    };

    static void Main (string [] args)
    {
        var statusList = new List<Building.StatusType> () { Building.StatusType.open, Building.StatusType.closed };
        var statusStringList = statusList.ConvertAll <string> (st => st.ToString ());

        var q = from building in buildingList
                where statusStringList.Contains (building.Status)
                select building;

        foreach ( var b in q )
            Console.WriteLine ("{0}: {1}", b.Name, b.Status);

        Console.ReadKey ();
    }

Saya membuat metode ekstensi ini untuk mengkonversi satu IEnumerable ke yang lain, tapi saya tidak yakin seberapa efisiennya; mungkin hanya membuat daftar di belakang layar.

public static IEnumerable <TResult> ConvertEach (IEnumerable <TSource> sources, Func <TSource,TResult> convert)
{
    foreach ( TSource source in sources )
        yield return convert (source);
}

Kemudian Anda dapat mengubah klausa tempat ke:

where statusList.ConvertEach <string> (status => status.GetCharValue()).
    Contains (v.Status)

dan lewati membuat List<string>dengan ConvertAll ()di awal.

Jika saya mengerti dengan benar, Anda perlu mengonversi tipe (nilai char) yang Anda simpan di daftar Bangunan ke tipe (enum) yang Anda simpan di daftar buildingStatus.

(Untuk setiap status dalam daftar Bangunan // nilai karakter //, apakah status ada di daftar buildingStatus // enum value //)

public static IQueryable<Building> WithStatus(this IQueryable<Building> qry,  
IList<BuildingStatuses> buildingStatus) 
{ 
    return from v in qry
           where ContainsStatus(v.Status)
           select v;
} 


private bool ContainsStatus(v.Status)
{
    foreach(Enum value in Enum.GetValues(typeof(buildingStatus)))
    {
        If v.Status == value.GetCharValue();
            return true;
    }

    return false;
}