.NET 6 web api: how to get raw the body content in controller

Question

I'm migrating a.NET 4.8 web API application to 6.0 but the snippet used to retrieve raw body content within a controller's method no longer works and always returns an empty string. By raw content I mean the whole json structure that is used to write a custom log. The.net 4.8 code, which runs within a post method, is as follows:

public async Task<IActionResult> PostAsync([FromBody] FooModel model)
{
    // some code
    string rawContent = string.Empty;
    using (var st = await this.Request.Content.ReadAsStreamAsync())
    {
       st.Seek(0, System.IO.SeekOrigin.Begin);
       using (var sr = new System.IO.StreamReader(st))
       {
            rawContent = sr.ReadToEnd();
       }
    }

    // some more code
}

In.net 6 I adapted it like this:

    string rawContent = string.Empty;
    using (var reader = new StreamReader(Request.Body,
                  encoding: Encoding.UTF8, detectEncodingFromByteOrderMarks: false))
    {
        rawContent  = await reader.ReadToEndAsync();
    }

Despite some adaptations I can not recover the data. Is there anyone who can give me directions? Thank you.

ste22

Maybe HttpResponseMessage.Content.ReadAsStringAsync() as a result of a HttpClient.SendAsync() — user743414, Oct 26 '22 at 07:09
Does the controller do any model binding before your lines of code? — monty, Oct 26 '22 at 07:14
@monty That assumes the body has been read though, right? Since you'd need to enable rewind if it hadn't. — ProgrammingLlama, Oct 26 '22 at 07:17
Could you please share the data part, which data you would like to bind? — Md Farid Uddin Kiron, Oct 26 '22 at 07:51
@ProgrammingLlama Not sure what `OP` wants to achieve, as you can see `rawContent` has set to empty nonetheless, it will return `''`. Therefore, I am not getting the expectations here. — Md Farid Uddin Kiron, Oct 26 '22 at 07:58
@ProgrammingLlama, how come, if we don't `assign any mdoel` on `rawContent` it will certainly return `''` isn't it? — Md Farid Uddin Kiron, Oct 26 '22 at 08:07
@Md Why do you keep mentioning models? That seems completely irrelevant here. — ProgrammingLlama, Oct 26 '22 at 08:09
No I mean something I need to assign on `rawContent` right? Otherthan it will always be empty. — Md Farid Uddin Kiron, Oct 26 '22 at 08:12
@Md It [works for me](https://i.stack.imgur.com/yDS91.png) in an ASP.NET Core 6 project when called from [Postman](https://i.stack.imgur.com/opJg9.png). — ProgrammingLlama, Oct 26 '22 at 08:13
Honestly, this also working on my side as well. However, not sure what `OP` is expecting. — Md Farid Uddin Kiron, Oct 26 '22 at 08:20
Yeah, nor me. The only thing I can think is that perhaps they also have a model binding (e.g. `[FromBody]SomeType someName` or `[FromForm]SomeType someName`) and then they're reading after ASP.NET Core has already read the stream without enabling buffering & rewinding the stream, but who knows at this stage. — ProgrammingLlama, Oct 26 '22 at 08:23
Yes ProgrammingLlama, you are right. The code uses model binding and I don't understand how to rewind the stream. With 4.8 I did it via seek but in 6.0 it gives me an error. I apologize for not being precise. — ste22, Oct 27 '22 at 09:48
I tried to enable buffering and to rewind the stream following the directions from this [url](https://stackoverflow.com/questions/21805362/rewind-request-body-stream) but it always returns an empty string. — ste22, Oct 27 '22 at 13:07
Could you please include your `program.cs` file? I can successfully get the body within your code, I just get get rid of `[FromBody] FooModel model` and working as expected. — Md Farid Uddin Kiron, Oct 31 '22 at 08:54
Hello, was the issue resolved? Have you tired the solution provided? Please let me know if any further assistance required on this. — Md Farid Uddin Kiron, Nov 02 '22 at 10:07
@Md Farid Uddin Kiron, you're right, the link indicates exactly how to do it; I had previously made a mistake. Thanks for everything to everyone. — ste22, Nov 02 '22 at 11:28

score 6 · Accepted Answer · answered Oct 31 '22 at 09:05

6

Web API application to 6.0 but the snippet used to retrieve raw body content within a controller's method no longer works and always returns an empty string.

Well, I have simulate the issue on dotnet 6 Web API project in following way, and I am getting the json which I am sending from PostMan

Controller:

    [HttpPost]
    public async Task<IActionResult> GetRawContent()
    {
        string rawContent = string.Empty;
        using (var reader = new StreamReader(Request.Body,
                      encoding: Encoding.UTF8, detectEncodingFromByteOrderMarks: false))
        {
            rawContent = await reader.ReadToEndAsync();
        }
       
        return Ok(rawContent);
       
    }

Output:

Simulation:

Note: As you are sending raw content so you can get rid of[FromBody] FooModel model as this only used when we explicitely use stricly typed model

answered Oct 31 '22 at 09:05

Md Farid Uddin Kiron

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this suggestion is also good; thanks for everything. – ste22 Nov 02 '22 at 11:30
I want to know why ASP.NET makes this so hard. It should be an utterly standard and trivially easy thing to do: there are situations where, for example, you are trying to handle a range of different object types, OR you are just trying to work out why the mapping isn't working the way you think it ought to. – Robbie Matthews May 29 '23 at 08:07
Hey, thanks for your response, not sure what's your concern and the context even what seems to your harder. In addition, It would be great if you could share your scenario in separate question thread so that it can be investigated accordingly. On top of this, based on scenario, reading request body may differ as numerous approach out there. – Md Farid Uddin Kiron May 29 '23 at 08:45
Right: Real world: I was chasing a problem where sometimes a POST was just not receiving anything in the body, just a null. It turned out there was ONE field in the json coming in as null, and the model definition did not allow for it. There was no meaningful error message anywhere I could find. Being able to examine what I was actually seeing would have made life much easier. – Robbie Matthews May 29 '23 at 09:26
Okay, thanks for the clarification, its depends on requirement and the approach. – Md Farid Uddin Kiron May 29 '23 at 09:52

score -1 · Answer 2 · answered May 29 '23 at 09:24

For 4.8 System.Web.Http.ApiController, this mostly works:

[HttpPost]
[Route("api/values/getrawcontent")]
public async Task<string> GetRawContent(int tag)
{
    string rawContent = await Request.Content.ReadAsStringAsync();
    return $"{tag}:rawContent}";
}

I say MOSTLY works, because all special characters seem to be escaped.

.NET 6 web api: how to get raw the body content in controller

2 Answers2