Function1.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Extensions.Logging;

namespace Test1
{
    public static class Function1
    {
        [FunctionName("Function1")]
        public static IActionResult Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] System.Collections.Immutable.ImmutableList<string> req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            return (req?.Count ?? 0) == 0
                ? (ActionResult)new OkObjectResult($"Hello, unknown")
                : new BadRequestObjectResult("Please pass a name on the query string or in the request body");
        }
    }
}

host.json

{
    "version": "2.0"
}

local.settings.json

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet"
    }
}

Test1.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <AzureFunctionsVersion>v2</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Http" Version="3.0.2" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.29" />
    <PackageReference Include="System.Collections.Immutable" Version="1.6.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>