The maximum size of object that can be passed as Parameter to POST method

Question

I have a web API controller with a POST method as follows.

public class MyController : ApiController
{
    // POST: api/Scoring
    public HttpResponseMessage Post([FromBody]MyClass request)
    {
        // some processing of request object
        return Request.CreateResponse(HttpStatusCode.OK, someResponseObject);
    }
    ....
}

This is consumed by a HTTPClient as follows

HttpClient httpClient = new HttpClient();
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
httpClient.BaseAddress = new Uri("http://localhost");
MyClass requestClient = new MyClass();
var task = httpClient.PostAsJsonAsync("api/my", requestClient)

It works great when MyObject object size passed in POST method parameter of controller is small in size. However in case when this object size is big, I get a null for the request object in the POST method parameters. In one case, the size of the requestClient object passed from client side request is ~5 MB and in the POST method, I get request object as null. Note that Web API is hosted under IIS. Is there any setting that I need to change for permissible size.

UPDATE: Adding following in web.config solved the null object issue in the POST method parameter.

httpRuntime maxRequestLength="2147483647" />

I then increased the size of requestClient object to ~50MB. Now the code in POST method never getting hit. On the client side, at the call to PostAsJsonAsyn, I get System.Net.HttpRequestException with following message.

Response status code does not indicate success: 404 (Not Found).

Now changing maxRequestLength doesn’t seem to have any impact.

Possible duplicate of [What is the size limit of a post request?](http://stackoverflow.com/questions/2364840/what-is-the-size-limit-of-a-post-request) — ssbb, Aug 15 '16 at 16:57
@ssbb Good point, however, this link doesn't provide me how to fix this for API hosted under IIS — paul deter, Aug 15 '16 at 17:00

score 12 · Accepted Answer · answered Aug 16 '16 at 16:04

From OP:

> then increased the size of requestClient object to ~50MB. Now the code in POST method never getting hit. On the client side, at the call to PostAsJsonAsyn, I get System.Net.HttpRequestException with following message.

Response status code does not indicate success: 404 (Not Found).

Now changing maxRequestLength doesn’t seem to have any impact.

When request filtering blocks an HTTP request because an HTTP request exceeds the request limits, IIS will return an HTTP 404 error to the client and log one of the following HTTP statuses with a unique substatus that identifies the reason that the request was denied:

 HTTP Substatus      Description
 404.13                 Content Length Too Large
 404.14                 URL Too Long
 404.15                 Query String Too Long
 ..etc

For Resolving the max limit issue, the Request Filtering role service(built-in security feature that was introduced in (IIS) 7.0 and above) should be configured: by SERVER MANAGER GUI or command utility appcmd.exe or modifying Web.config

    <configuration>
       <system.webServer>
          <security>
             <requestFiltering>
                 .....

                <!-- limit post size to 10mb, query string to 256 chars, url to 1024 chars -->
                <requestLimits maxQueryString="256" maxUrl="1024" maxAllowedContentLength="102400000" />

                .....
             </requestFiltering>
          </security>
       </system.webServer>
    </configuration>

For Configuration details review :

https://www.iis.net/configreference/system.webserver/security/requestfiltering

The maximum size of object that can be passed as Parameter to POST method

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