C# - 在 Linq Where Any 语句中使用的要列出的字符串

Question

我想使用这个字符串作为过滤器来删除 linq 查询中的一些 ID

public class ProductKitMakerDto
{
    public int Id { get; set; }
    public string TitleShort { get; set; }
    public string Media { get; set; }
}

[HttpPost]
public ActionResult KitItemSelect(string culture)
{
    string productMakerIds = "4174,2196,2201,2460,2508,2204";

    //create a list
    var productMakerList = new List<ProductKitMakerDto>();
    foreach (int i in productMakerIds)
    {
        productMakerList.Add(new ProductKitMakerDto { Id = i });
    }

    var itemselects = (from p in _context.Products
                   where p.Matrix == 2400
                   select new ProductKitMakerDto()
                   {
                   Id = p.Id,
                   TitleShort = culture == "de" ? p.TitleShortDe :
                                culture == "fr" ? p.TitleShortFr :
                                p.TitleShortEn,
                    Media = "/img/" + p.Photo,
                    }).ToList();

    //From this query I get 40 results.
    //Then I want to remove the ones from the list:

    //itemselects = itemselects.Where(i => !productMakerList.Any(pml =>pml.Id == i.Id));

    //1st (above) I get an Error CS0266 asking for explicit cast. So aplly the modification

    itemselects = (List<ProductKitMakerDto>)itemselects.Where(i => !productMakerList.Any(pml =>pml.Id == i.Id));

    return Json(itemselects, JsonRequestBehavior.AllowGet);
}

我收到 500（内部服务器错误）- xhr.send( options.hasContent && options.data || null ); 我猜列表是空的。任何想法？谢谢

Answer 1

foreach (string i in productMakerIds.Split(','))
    {
        productMakerList.Add(new ProductKitMakerDto { Id = int.Parse(i) });
    }

Answer 2

这行不通

string productMakerIds = "4174,2196,2201,2460,2508,2204";
var productMakerList = new List<ProductKitMakerDto>();
foreach (int i in productMakerIds)
{
    productMakerList.Add(new ProductKitMakerDto { Id = i });
}

因为你需要先用逗号分割然后将 string 解析为 int:

   foreach (string i in productMakerIds.Split(',')) // and parse i to int with int.Parse

但是因为它是一个字符串文字，所以首先要正确地初始化它。不要使用 List<ProductKitMakerDto> 因为你只需要一个 List<int>，那么你可以使用 Contains:
```
var productMakerList = new List<int>
{
    4174, 2196, 2201, 2460, 2508 , 2204
};
```

如果它不是列表并且 Enumerable.Where 不是 return 一个：

，则不能转换为列表

itemselects = (List<ProductKitMakerDto>)itemselects.Where(i => !productMakerList.Any(pml =>pml.Id == i.Id));

您需要在 Where

之后附加 ToList

   itemselects = itemselects
       .Where(i => !productMakerList.Any(pml =>pml.Id == i.Id))
       .ToList();

但如前所述，您也可以在第一次创建该列表之前使用此 Where，因此请在 Contains 中包含应支持的条件：

var itemselects = (from p in _context.Products
                   where p.Matrix == 2400
                   && !productMakerList.Contains(p.Id)
                   select new ProductKitMakerDto()
                   {
                      Id = p.Id,
                      TitleShort = culture == "de" 
                         ? p.TitleShortDe 
                         : culture == "fr" ? p.TitleShortFr : p.TitleShortEn,
                      Media = "/img/" + p.Photo,
                   }).ToList();

C# - 在 Linq Where Any 语句中使用的要列出的字符串

C# - String to list used in Linq Where Any statement

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