How can I get object by specific parameter in GrahpQl with HotChocolate C#

Question

I am using HotChocolate library to work with GraphQL via .NET. I already can get all objects, that are stored in db, using this query:

query 
{
    news
    {
        title
        description
    }
}

But I need to have an opportunity, to select object with specific id like in this query:

query
{
    news(id: 5) 
    {
        title
        description
    }
}

But I'm getting the following exception

Unknown argument "id" on field "Query.news".

I use this code to get all news from database and return it to a client:

    [UseDbContext(typeof(Context.Context))]
    [UseFiltering]
    [UseSorting]
    public IQueryable<Entities.News> GetNews([ScopedService] Context.Context context)
    {
        return context.News;
    }

Also I tried to get an object by id using this code:

    [UseDbContext(typeof(Context.Context))]
    [UseFiltering]
    [UseSorting]
    public Entities.News GetNews(int id, [ScopedService] Context.Context context)
    {
        return context.News.Find(id);
    }

But I іtill have the exception when trying to get it by id

Is you question about specifying the ID in Graph Query, or when getting data from DB? — Chris Hammond, Jun 07 '22 at 06:20
@ChrisHammond I mean, I want to have an opportunity to send query, where I can write news(id:4){name}, and I will have name for news with id 4, and now if I will write such query, I will have an exeption in graphQl. Query dont understand what "id" is — andruhevich, Jun 07 '22 at 22:26
Please add the class definition of `Context.Context.News` to your question — Chris Hammond, Jun 09 '22 at 05:58
It sounds like your schema definition is not exposing as expected — Chris Hammond, Jun 09 '22 at 05:59

Chris Hammond · Answer 1 · 2022-06-07T06:14:12.273

0

With the UseFiltering attribute, this exposes a new schema "descriptor" of WHERE and you can then use this in your Graph QL query

query ($searchId: Int!)
{
    news(where: {id: {eq:  $searchId}}) 
    {
        title
        description
    }
}
variables {
    "searchId" : 1
}

edited Jun 07 '22 at 06:14

answered May 31 '22 at 13:39

Chris Hammond

2,064
5
27
53

I know about this feature, but I need to take this as a parameter – andruhevich Jun 05 '22 at 12:15
@andruhevich - You can define `variables` in the query body - I have updated my answer – Chris Hammond Jun 07 '22 at 06:14
Sorry, but it still not what I'm looking for – andruhevich Jun 07 '22 at 22:28

score 0 · Answer 2 · answered Jul 28 '22 at 11:15

The short answer: no, you cannot proceed that way.

The explanation: the attribute [UseFiltering] can be applied to something that presents a collection of items only. In the second method with 'id', you are trying to return the single entity along with [UseFiltering]. It's not possible.

So, in total, you have the following options (which all do not conform to your needs exactly):

You follow the way in that answer - as for me, it is the most logically correct approach.
You can add the parameter 'id' to the method GetNews but still return IQueryable containing the single element or nothing - as for me, the most non-intuitive approach because the selection by single id is logically incompatible with filtering by WHERE, results ordering and pagination.
Create a separate method GetUserById returning a single element - as for me, the correct approach which is often used along with p.1.

How can I get object by specific parameter in GrahpQl with HotChocolate C#

2 Answers2