Asp.net: 'application/grpc-web' is not supported

Question

I had Asp.net core and gRPC working on the browser...but now I get:

info: Grpc.AspNetCore.Server.ServerCallHandler[2]
  Request content-type of 'application/grpc-web' is not supported.

Any ideas on how to track this down?

Have you done any changes to the project and then this started to happen or did all this just happen by it self all of the sudden? — Michel Jansson, Dec 05 '20 at 20:56
Ok @Ray, I believe you have to give up some more info to have any chance of help.. — Michel Jansson, Dec 07 '20 at 16:28
Wish I could've given more info that would have been useful. I was looking for more diagnostics that would point to the problem. Like listing supported content-types, etc... Anyway, I found the problem: I called app.UseEndpoints() twice is...bad? — Ray, Dec 07 '20 at 19:03
BTW: I've added a unit test that catches this kinda error quicker. — Ray, Dec 07 '20 at 19:07

score 13 · Answer 1 · answered Feb 25 '21 at 05:20

13

Likely an issue in your Startup.cs

Yours should look something like this

My guess is that you are missing app.UseGrpcWeb() or the EnabledGrpc() on the EndpointConventionBuilder

answered Feb 25 '21 at 05:20

thalacker

1

You saved my day! The only thing that I needed to change here are cors settings and to set it like here https://learn.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-6.0 – Vahid Feb 24 '22 at 23:59

score 7 · Answer 2 · answered Mar 23 '21 at 16:02

I ran across this issue. I had my app.UseGrpcWeb(); before app.UseRouting();

It had to be after.

So correct order is:

    app.UseRouting();
    app.UseGrpcWeb();

2 Answers2