Open API Extension to Support Azure Functions v1

01-v1-legacy.cs

namespace MyV1LegacyFunctionApp
{
    public static class LoremIpsumHttpTrigger
    {
        [FunctionName("LoremIpsumHttpTrigger")]
        public static async Task<HttpResponseMessage> Run(
            [HttpTrigger(AuthorizationLevel.Function, "GET", Route = "lorem/ipsum")] HttpRequestMessage req,
            ILogger log)
        {
            var content = new MyReturnObject();

            var result = req.CreateResponse(HttpStatusCode.OK, content);

            return await Task.FromResult(result).ConfigureAwait(false);        }
    }
}

02-v1-proxy.cs

namespace MyV1ProxyFunctionApp
{
    public static class LoremIpsumHttpTrigger
    {
        [FunctionName("LoremIpsumHttpTrigger")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "GET", Route = "lorem/ipsum")] HttpRequest req,
            ILogger log)
        {
            return await Task.FromResult(new OkResult()).ConfigureAwait(false);
        }
    }
}

03-v1-proxy-openapi.cs

namespace MyV1ProxyFunctionApp
{
    public static class LoremIpsumHttpTrigger
    {
        [OpenApiOperation(operationId: "getIpsum", tags: new[] { "ipsum" }, Summary = "Gets Ipsum from Lorem", Description = "This gets Ipsum from Lorem.", Visibility = OpenApiVisibilityType.Important)]
        [OpenApiParameter(name: "name", In = ParameterLocation.Query, Required = true, Type = typeof(string), Summary = "Lorem name", Description = "Lorem name", Visibility = OpenApiVisibilityType.Important)]
        [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "application/json", bodyType: typeof(MyReturnObject), Summary = "The Ipsum response", Description = "This returns the Ipsum response")]
        [OpenApiResponseWithoutBody(statusCode: HttpStatusCode.NotFound, Summary = "Name not found", Description = "Name parameter is not found")]
        [OpenApiResponseWithoutBody(statusCode: HttpStatusCode.BadRequest, Summary = "Invalid Lorem", Description = "Lorem is not valid")]

        [FunctionName("LoremIpsumHttpTrigger")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "GET", Route = "lorem/ipsum")] HttpRequest req,
            ILogger log)
        {
            return await Task.FromResult(new OkResult()).ConfigureAwait(false);
        }
    }
}

04-proxies.json

{
  "$schema": "http://json.schemastore.org/proxies",
  "proxies": {
    "LoremIpsumHttpTriggerProxy": {
      "matchCondition": {
        "route": "/api/lorem/ipsum",
        "methods": [
          "GET"
        ]
      },
      "backendUri": "https://mylegacyfunctionapp.azurewebsites.net/api/lorem/ipsum",
      "requestOverrides": {
        "backend.request.headers": "{request.headers}",
        "backend.request.querystring": "{request.querystring}"
      }
    }
  }
}

05-v1-proxy.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
    ...
  </PropertyGroup>
  ...
  <ItemGroup>
    ...
    <None Update="proxies.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>
  ...
</Project>