The .NET gRPC client can be configured to make gRPC-Web calls. This is useful for Blazor WebAssembly apps, which are hosted in the browser and have the same HTTP limitations of JavaScript code. Calling gRPC-Web with a .NET client is the same as HTTP/2 gRPC. The only modification is how the channel is created.
To use gRPC-Web:
- Add a reference to the Grpc.Net.Client.Web package.
- Ensure the reference to Grpc.Net.Client package is 2.29.0 or greater.
- Configure the channel to use the
GrpcWebHandler
:
var channel = GrpcChannel.ForAddress("https://localhost:5001", new GrpcChannelOptions
{
HttpHandler = new GrpcWebHandler(new HttpClientHandler())
});
var client = new Greeter.GreeterClient(channel);
var response = await client.SayHelloAsync(new HelloRequest { Name = ".NET" });
The preceding code:
- Configures a channel to use gRPC-Web.
- Creates a client and makes a call using the channel.
GrpcWebHandler
has the following configuration options:
- InnerHandler: The underlying
HttpMessageHandler
that makes the gRPC HTTP request, for example,HttpClientHandler
. - GrpcWebMode: An enumeration type that specifies whether the gRPC HTTP request
Content-Type
isapplication/grpc-web
orapplication/grpc-web-text
.GrpcWebMode.GrpcWeb
configures content to be sent without encoding. Default value.GrpcWebMode.GrpcWebText
configures content to be base64 encoded. Required for server streaming calls in browsers.
- HttpVersion: HTTP protocol
Version
used to setHttpRequestMessage.Version
on the underlying gRPC HTTP request. gRPC-Web doesn't require a specific version and doesn't override the default unless specified.
Traditional gRPC over HTTP/2 supports streaming in all directions. gRPC-Web offers limited support for streaming:
- gRPC-Web browser clients don't support calling client streaming and bidirectional streaming methods.
- gRPC-Web .NET clients don't support calling client streaming and bidirectional streaming methods over HTTP/1.1.
- ASP.NET Core gRPC services hosted on Azure App Service and IIS don't support bidirectional streaming.
When using gRPC-Web, we only recommend the use of unary methods and server streaming methods.