Azure Functions HTTP Orchestration Trigger with multipart/form-data

In this post, let's see have how we can invoke a HTTP Orchestration Trigger in an Azure Durable Functions with multipart/form-data. There can be scenarios where you want to pass multipart/form-data (mostly files) to HTTP Orchestration Trigger.

Note I am using Azure Functions Isolated model.

If you scaffold a a Durable Function in Visual Studio, you will see it's HTTP Trigger function to be something like below.

[Function("Function_HttpStart")]
public static async Task<HttpResponseData> HttpStart(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req,
    [DurableClient] DurableTaskClient client,
    FunctionContext executionContext)
{
    string instanceId = await client.ScheduleNewOrchestrationInstanceAsync(nameof(Function));
        
    // Omitted for brevity.
        
    return await client.CreateCheckStatusResponseAsync(req, instanceId);
}

Notice that it uses HttpRequestData for request and for HttpResponseData. which is available via,

Microsoft.Azure.Functions.Worker.Extensions.Http

Instead of these, we can make use of Azure Functions ASP.NET Core integration and start using ASP.NET Core Request/Response types including HttpRequest, HttpResponse and IActionResult in HTTP Triggers.

Azure Functions ASP.NET Core integration is available via following NuGet package.

Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore

And then in the Program.cs,

FunctionsApplicationBuilder builder = FunctionsApplication.CreateBuilder(args);
 
// Enable ASP.NET Core features in Azure Functions
builder.ConfigureFunctionsWebApplication();

// Omitted for brevity

And now we can change the HTTP trigger as follows.

[Function("Function_HttpStart")]
public static async Task<IActionResult> HttpStart(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req,
    [DurableClient] DurableTaskClient client,
    FunctionContext executionContext)
{
    string instanceId = await client.ScheduleNewOrchestrationInstanceAsync(nameof(Function));
 
    if (req.HasFormContentType)
    {
        IFormCollection formCollection = await req.ReadFormAsync();
        // TODO: Process form data as needed.
    }
 
    // Omitted for brevity.
 
    HttpManagementPayload httpManagementPayload = client.CreateHttpManagementPayload(instanceId);
    return new ObjectResult(httpManagementPayload)
    {
        StatusCode = (int)HttpStatusCode.Accepted
    };
}

By the way, if you want to use multipart/form-data in any of the Azure Functions HTTP Triggers, Azure Functions ASP.NET Core integration is the way. 

Hope this helps.

Happy Coding.

Regards,

Jaliya