C# web api 獲取請求失敗或添加額外信息

Question

我遇到了問題。 我有這些課程。

public class VariantColor
{
    public int Id { get; set; }
    public string Name { get; set; }
    [JsonIgnore]
    public IEnumerable<ProductVariant> productVariants { get; set; }
}

public class VariantSize
    {
        public int Id { get; set; }
        public string Name { get; set; }
        [JsonIgnore]
        public IEnumerable<ProductVariant> productVariants { get; set; }
    }

我將它們添加到 dbcontext

public DbSet<VariantColor> variantColors { get; set; }
public DbSet<VariantSize> variantSizes { get; set; }

我在 VariantSizeRepository 中有這個，它工作正常。

public async Task<IEnumerable<VariantSize>> GetAllSizes()
        {
            var sizes = await _dataContext.variantSizes.ToListAsync();

            if(sizes == null)
            {
                return null;
            }

            return sizes;
        }

但是我在 VariantColorRepository 中有幾乎相同的調用

 public async Task<IEnumerable<VariantColor>> GetVariantColors()
    {
        var colors =  _dataContext.variantColors.ToList();
        if (colors == null)
        {
            return null;
        }

        return colors;
    }

如果我使用 ToList() 而不是異步版本，我會收到帶有額外代碼的響應

{
  "result": [
    {
      "id": 1,
      "name": "red"
    },
    {
      "id": 2,
      "name": "green"
    }
  ],
  "id": 242,
  "exception": null,
  "status": 5,
  "isCanceled": false,
  "isCompleted": true,
  "isCompletedSuccessfully": true,
  "creationOptions": 0,
  "asyncState": null,
  "isFaulted": false
}

如果我使用 ToListAsync() 它會拋出錯誤

System.NotSupportedException: Serialization and deserialization of 'System.Action' instances are not supported. Path: $.MoveNextAction.
 ---> System.NotSupportedException: Serialization and deserialization of 'System.Action' instances are not supported.
   at System.Text.Json.Serialization.Converters.UnsupportedTypeConverter`1.Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)

我無法弄清楚問題所在，我將這些調用與 VariiantSizes 進行了相同的調用，但它會拋出錯誤……我做錯了什么？

Answer 1

在這段代碼中

public async Task<IEnumerable<VariantColor>> GetVariantColors()
    {
        var colors =  _dataContext.variantColors.ToList();
        if (colors == null)
        {
            return null;
        }

        return colors;
    }

回報

IEnumerable<VariantColor>

不是

Task<IEnumerable<VariantColor>>

不出所料

改變

var colors =  _dataContext.variantColors.ToList();

改為

var colors =  await  _dataContext.variantColors.ToListAsync();