Register converter in extension methods

Author: JannikLassahn

README.md

@@ -29,19 +29,7 @@ public void Configure(IApplicationBuilder app)
 }
 ```
 
-Register the converter in your schema.
-```csharp
-public class MySchema : Schema
-{
-  public MySchema()
-  {
-    RegisterValueConverter(new FormFileConverter());
-    // ...
-  }
-}
-```
-
-Finally, use the upload scalar in your resolvers. Files are exposed as `IFormFile`. 
+Use the upload scalar in your resolvers. Files are exposed as `IFormFile`. 
 ```csharp
 Field<StringGraphType>(
     "singleUpload",

src/GraphQL.Upload.AspNetCore/ApplicationBuilderExtensions.cs

@@ -40,6 +40,13 @@ public static IApplicationBuilder UseGraphQLUpload<TSchema>(this IApplicationBui
             if (options is null)
                 throw new ArgumentNullException(nameof(options));
 
+            var schema = (TSchema)builder.ApplicationServices.GetService(typeof(TSchema));
+
+            if (schema == null)
+                throw new ArgumentException($"No service type for {typeof(TSchema).FullName} registered.");
+
+            schema.RegisterValueConverter(new FormFileConverter());
+
             return builder.UseWhen(context => context.Request.Path.StartsWithSegments(path), branch => branch.UseMiddleware<GraphQLUploadMiddleware<ISchema>>(options));
         }
     }

tests/GraphQL.Upload.AspNetCore.Tests/TestSchema.cs

@@ -9,8 +9,6 @@ public class TestSchema : Schema
     {
         public TestSchema()
         {
-            RegisterValueConverter(new FormFileConverter());
-
             Query = new Query();
             Mutation = new Mutation();
         }