File Upload with Relay and graphql-dotnet

Question

I'm trying to build a mutation within relay that includes a file. As soon as I implement the getFiles() method referenced here: https://facebook.github.io/relay/docs/api-reference-relay-mutation.html#getfiles

Relay sends a multipart request causing a 415 error from ASP.NET Core MVC.

I'm looking for a working example, similar to "How would you do file uploads in a React-Relay app?" with the graphql-dotnet library.

Answer 1

The GraphQL Endpoint wasn't accepting the multi-part form mimetype because it wasn't JSON. I was able to work with the files once I got them into graphql-dotnet via the RootObject and the context that's available in the mutation. What was throwing me off was MVC.

So I wrote a simple Filter:

public class RelayResourceFilter : IResourceFilter
{
    private readonly string jsonMediaType = "application/json";

    public void OnResourceExecuted(ResourceExecutedContext context)
    {
    }

    public void OnResourceExecuting(ResourceExecutingContext context)
    {


        if (!string.Equals(MediaTypeHeaderValue.Parse(context.HttpContext.Request.ContentType).MediaType,
            this.jsonMediaType, StringComparison.OrdinalIgnoreCase))
        {
            var encoder = JavaScriptEncoder.Create();
            var variables = encoder.Encode(context.HttpContext.Request.Form["variables"]);
            var query = encoder.Encode(context.HttpContext.Request.Form["query"]);
            var body = $"{{\"query\":\"{query}\", \"variables\":\"{variables}\"}}";

            byte[] requestData = Encoding.UTF8.GetBytes(body);
            context.HttpContext.Request.Body = new MemoryStream(requestData);
            context.HttpContext.Request.ContentType = this.jsonMediaType;
        }
    }
}

registered it:

services.AddScoped<RelayResourceFilter>();

and then applied it like so in the Controller:

[ServiceFilter(typeof(RelayResourceFilter))]
    public async Task<ExecutionResult> Post([FromBody]GraphQLQuery query, bool? useErrorCode)
{
var files = this.Request.HasFormContentType ? this.Request.Form.Files : null;
// ... assignment to Root Object
}