Question 87964 in ASP.NET Question posted in
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Is it possile to return .NET object from controller to middleware – Asp.net

I was working on one of the requirements, where I need to modify result data in middleware (not any MVC Filters due to some other services injected through middleware).

In middleware I was getting data in json format and then deserializing that data then updating that data and finally serializing to JSON and sending it back as a response.

I don’t want to serialize data in MVC pipeline so I tried to remove output formator but that didn’t work for me and throwing error.

services.AddControllers(options =>
        {
            options.OutputFormatters.Clear();
        });

Is there any solution to get the .Net object in the pipeline and modify that object (as we do in MVC filter) and then serialize at last?

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4

Answers


  1. 0

    I am not sure whether it fits your requirements but you can use HttpContext to store some data in the scope of the request. There is a ‘Items’ key-value collection.

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  2. 0

    Beside the other suggestion to use Items of HttpContext, I want to note that you can inject services into Action Filters:

    public class ResultFilter : IActionFilter
{

    // Inject anything you want
    IHostEnvironment env;
    public ResultFilter(IHostEnvironment env)
    {
        this.env = env;
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
        if (context.Result is OkObjectResult result)
        {
            result.Value = JsonSerializer.Serialize(new
            {
                Value = result.Value,
                Environment = this.env.EnvironmentName,
            });
        }
    }

    public void OnActionExecuting(ActionExecutingContext context) { }
}

    Register to DI Builder:

    services.AddScoped<ResultFilter>();

    Apply to action/controller:

        [HttpGet, Route("/test"), ServiceFilter(typeof(ResultFilter))]
    public IActionResult ReturnOk()
    {
        return this.Ok(new
        {
            Value = 1,
        });
    }

    Testing by accessing the URL:

    {"Value":{"Value":1},"Environment":"Development"}
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  3. 0

    Another alternative is to use DI service with Scoped lifetime.

    Scoped objects are the same for a given request but differ across each new request.

    Service:

    public interface IMyRequestDataService
{
    object? MyData { get; set; }
}

public class MyRequestDataService : IMyRequestDataService
{

    public object? MyData { get; set; }

}

    Register to DI:

    services.AddScoped<IMyRequestDataService, MyRequestDataService>();

    Set data in Controller:

        readonly IMyRequestDataService dataService;
    public TestController(IMyRequestDataService dataService)
    {
        this.dataService = dataService;
    }

    [HttpGet, Route("/test-scoped")]
    public IActionResult ReturnObj()
    {
        this.dataService.MyData = new
        {
            Value = 1,
        };

        return this.Ok();
    }

    Your middleware that consumes it:

    class CustomMiddleware
{
    readonly RequestDelegate next;
    public CustomMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    // Add DI Services here
    public async Task InvokeAsync(HttpContext httpContext, IMyRequestDataService dataService, IHostEnvironment env)
    {
        await this.next(httpContext);

        // Data should be here
        if (dataService.MyData != null)
        {
            // Do something with it
            await httpContext.Response.WriteAsJsonAsync(new
            {
                Data = dataService.MyData,
                Env = env.EnvironmentName,
            });
        }
    }

}

// Register it:
app.UseMiddleware<CustomMiddleware>();

// Make sure it's before the Controller middleware since we wrap it around the next()
// ...

app.MapControllers();

    Test with the URL:

    {"data":{"value":1},"env":"Development"}
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  4. 0

    You can store data in HTTP context items.

    In controller action:

    Request.HttpContext.Items.Add("SomeKey", data);

    In middleware:

    object data = httpContext.Items["SomeKey"];
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