asp.net - GraphQL.NET 如何将枚举添加到 GraphQL 类型

Question

我有一个简单的枚举，我试图将其包含在我的 GraphQL 类型中，但收到以下错误:

The GraphQL type for Field: 'Category' on parent type: 'NewsItemType' could not be derived implicitly.

------------------The GraphQL type for Field: 'Category' on parent type: 'NewsItemType' could not be derived implicitly.

---------------The type: NewsType cannot be coerced effectively to a GraphQL type Parameter name: type

我的简单枚举看起来像:

public enum NewsType
{
    General = 0,

    Business = 1,

    Entertainment = 2,

    Sports = 3,

    Technology = 4
}

GraphQL ObjectGraphType它包含在:

public class NewsItemType : ObjectGraphType<NewsItemViewModel>
{
    public NewsItemType()
    {
        Field(x => x.Id).Description("Id of a news item.");
        Field(x => x.Title).Description("Title of a new item.");
        Field(x => x.Description).Description("Description of a news item.");
        Field(x => x.Author).Description("Author of a news item.");
        Field(x => x.Url).Description("URI location of the news item");
        Field(x => x.ImageUrl).Description("URI location of the image for the news item");
        Field(x => x.PublishDate).Description("Date the news item was published");
        Field(x => x.Category).Description("Category of the news item.");
    }
}

最后，graphql 类型基于的 View 模型:

public class NewsItemViewModel : ViewModelBase
{
    public string Title { get; set; }

    public string Author { get; set; }

    public string Description { get; set; }

    public string Url { get; set; }

    public string ImageUrl { get; set; }

    public DateTime PublishDate { get; set; }

    public NewsType Category { get; set; }
}

我在这里做错了什么，我该如何克服它？
编辑:
我的查询包含以下内容:

        Field<ListGraphType<NewsItemType>>(
            name: "newsItems",
            arguments: new QueryArguments(
                new QueryArgument<IntGraphType>() { Name = "count" },
                new QueryArgument<IntGraphType>() { Name = "category" }),
            resolve: context =>
            {
                var count = context.GetArgument<int?>("count");
                var category = context.GetArgument<int>("category");
                var newsType = (NewsType)category;

                if (count.HasValue)
                {
                    return newsItemService.GetMostRecent(newsType, count.Value);
                }
                else
                {
                    return newsItemService.GetMostRecent(newsType);
                }
            }
        )

Answer 1

我也很难让它发挥作用。在这方面，官方文档似乎肯定是缺乏的。我让它工作的方式是基于我在 this article 中找到的东西.

对于您的场景，您将为您的枚举创建一个“GraphType”类，如下所示:

public class NewsEnumType : EnumerationGraphType<NewsType>
{
}

然后将您的字段更新为:

Field<NewsEnumType>(nameof(NewsItemViewModel.Category)).Description("Category of the news item.");

还有一件事要提到，我遇到了我没想到的 EnumTypes。如果您使用枚举作为参数，请执行您在上面将其作为 IntGraphType 摄取的操作。然后将其转换为您的枚举类型 (NewsType)category

    Field<ListGraphType<NewsItemType>>(
        name: "newsItems",
        arguments: new QueryArguments(
            new QueryArgument<IntGraphType>() { Name = "count" },
            new QueryArgument<IntGraphType>() { Name = "category" }),
        resolve: context =>
        {
            var count = context.GetArgument<int?>("count");
            var category = context.GetArgument<int>("category");
            var newsType = (NewsType)category;

            if (count.HasValue)
            {
                return newsItemService.GetMostRecent(newsType, count.Value);
            }
            else
            {
                return newsItemService.GetMostRecent(newsType);
            }
        }
    )

我的枚举是我作为参数传递的复杂对象的一部分，更像是 new QueryArgument<NewsItemType>() { Name = "newsItem" },
如果您打算这样做，那么 category传递给服务器的对象上的属性需要是一个字符串。因此，如果您传回服务器的类别是 Business = 1 ，那么你需要通过 category: 'Business'而不是 category: 1 .