c#在select linq to array中替换null

bttbmeg0  于 2023-03-27  发布在  C#
关注(0)|答案(2)|浏览(140)
var eans = myDeserializedClass.listings
     .Select(x => new {  x.amount, x.variant.variantName ?? " "})
     .Where(x => x.variantName != null)
     .ToArray();

上面的代码不起作用。在这种情况下,我如何替换空值?

x.variant.variantName ?? " "

当我创建??““时出现错误。x1c 0d1x
非常类似的代码与字段的名称(如图所示)编译得很好:

var eans = myDeserializedClass.listings
     .Select(x => new {  x.amount, V = x.variant.variantName ?? " "})
     .Where(x => x.V != null)
     .ToArray();

我尝试了很多东西,但无法找到解决方案来替换此选择中的空值
类看起来像:

public class Ask888
    {
        public string askId { get; set; }
        public DateTime askCreatedAt { get; set; }
        public DateTime askUpdatedAt { get; set; }
        public DateTime askExpiresAt { get; set; }
    }

    public class Listing888
    {
        public string listingId { get; set; }
        public string status { get; set; }
        public string amount { get; set; }
        public string currencyCode { get; set; }
        public string inventoryType { get; set; }
        public DateTime createdAt { get; set; }
        public DateTime updatedAt { get; set; }
        public Product888 product { get; set; }
        public Variant888 variant { get; set; }
        public object batch { get; set; }
        public Ask888 ask { get; set; }
        public object order { get; set; }
    }

    public class Product888
    {
        public string productId { get; set; }
        public string productName { get; set; }
    }

    public class Root888
    {
        public int count { get; set; }
        public int pageNumber { get; set; }
        public int pageSize { get; set; }
        public bool hasNextPage { get; set; }
        public List<Listing888> listings { get; set; }
    }

    public class Variant888
    {
        public string variantId { get; set; }
        public string variantName { get; set; }
        public string variantValue { get; set; }
    }

最后我就这样一直犯错误;/

string json = response.Content.ToString();
    
var settings = new JsonSerializerSettings
                {
                    NullValueHandling = NullValueHandling.Ignore,
                    MissingMemberHandling = MissingMemberHandling.Ignore
                };
    
    
Root888 myDeserializedClass = JsonConvert.DeserializeObject<Root888>(json, settings);
    
    
    
    
var eans = myDeserializedClass.listings
.Select(x => new { x.listingId, x.product.productId, x.status, x.amount, variantName = x.variant.variantName ?? " ", variantId = x.variant.variantId ?? " ", variantValue = x.variant.variantValue ?? " " })
.ToArray();

错误仍然

aoyhnmkz

aoyhnmkz1#

问题是variant为null,因此无法获取null对象的变量名
你有代码:

var eans = myDeserializedClass.listings
 .Select(x => new {  x.amount, V = x.variant.variantName ?? " "})
 .Where(x => x.V != null)
 .ToArray();

这只处理variantName为null的情况。但是包含variantName的父对象呢?如果它为null呢?
将其改为在variantName之前使用?.。然后,如果变量为null,则null传播运算符??实际上有一些可用的东西可以使用。
这应该行得通:

var eans = myDeserializedClass.listings
 .Select(x => new {  x.amount, V = x.variant?.variantName ?? " "})
 .Where(x => x.V != null)
 .ToArray();
wvt8vs2t

wvt8vs2t2#

您需要命名匿名类型的成员:

var eans = myDeserializedClass.listings
                       .Select(x => new { x.listingId, x.product.productId, x.status, x.amount, variantName = x.variant.variantName ?? " ",x.variant.variantId, x.variant.variantValue }).Where(x => x.variantName != null)
                       .ToArray();

关键点:
variantName = x.variant.variantName??““

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