How to get POST data in WebAPI?

Question

I\'m sending a request to server in the following form:

http://localhost:12345/api/controller/par1/par2

The request is correctly resolved t

Answer 1

After spending a good bit of time today trying to wrap my brain around the (significant but powerful) paradigm shift between old ways of processing web form data and how it is done with WebAPI, I thought I'd add my 2 cents to this discussion.

What I wanted to do (which is pretty common for web form processing of a POST) is to be able to grab any of the form values I want, in any order. Say like you can do if you have your data in a System.Collections.Specialized.NameValueCollection. But turns out, in WebAPI, the data from a POST comes back at you as a stream. So you can't directly do that.

But there is a cool little class named FormDataCollection (in System.Net.Http.Formatting) and what it will let you do is iterate through your collection once.

So I wrote a simple utility method that will run through the FormDataCollection once and stick all the values into a NameValueCollection. Once this is done, you can jump all around the data to your hearts content.

So in my ApiController derived class, I have a post method like this:

    public void Post(FormDataCollection formData)
    {
        NameValueCollection valueMap = WebAPIUtils.Convert(formData);

        ... my code that uses the data in the NameValueCollection
    }

The Convert method in my static WebAPIUtils class looks like this:

    /// <summary>
    /// Copy the values contained in the given FormDataCollection into 
    /// a NameValueCollection instance.
    /// </summary>
    /// <param name="formDataCollection">The FormDataCollection instance. (required, but can be empty)</param>
    /// <returns>The NameValueCollection. Never returned null, but may be empty.</returns>
    public static NameValueCollection Convert(FormDataCollection formDataCollection)
    {
        Validate.IsNotNull("formDataCollection", formDataCollection);

        IEnumerator<KeyValuePair<string, string>> pairs = formDataCollection.GetEnumerator();

        NameValueCollection collection = new NameValueCollection();

        while (pairs.MoveNext())
        {
            KeyValuePair<string, string> pair = pairs.Current;

            collection.Add(pair.Key, pair.Value);
        }

        return collection;
     }

Hope this helps!

Answer 2

Try this.

public string Post(FormDataCollection form) {
    string par1 = form.Get("par1");

    // ...
}

It works for me with webapi 2

Answer 3

I found for my use case this was much more useful, hopefully it helps someone else that spent time on this answer applying it

public IDictionary<string, object> GetBodyPropsList()
        {
            var contentType = Request.Content.Headers.ContentType.MediaType;
            var requestParams = Request.Content.ReadAsStringAsync().Result;

            if (contentType == "application/json")
            {
                return Newtonsoft.Json.JsonConvert.DeserializeObject<IDictionary<string, object>>(requestParams);
            }
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }

Answer 4

None of the answers here worked for me. Using FormDataCollection in the post method seems like the right answer but something about my post request was causing webapi to choke. eventually I made it work by including no parameters in the method call and just manually parsing out the form parameters like this.

public HttpResponseMessage FileUpload() {
    System.Web.HttpRequest httpRequest = System.Web.HttpContext.Current.Request;
    System.Collections.Specialized.NameValueCollection formData = httpRequest.Form;
    int ID = Convert.ToInt32(formData["ID"]);
    etc

Answer 5

Is there a way to handle form post data in a Web Api controller?

The normal approach in ASP.NET Web API is to represent the form as a model so the media type formatter deserializes it. Alternative is to define the actions's parameter as NameValueCollection:

public void Post(NameValueCollection formData)
{
  var value = formData["key"];
}

Answer 6

From answer in this question: How to get Json Post Values with asp.net webapi

1. Autoparse using parameter binding; note that the dynamic is made up of JToken, hence the .Value accessor.

   public void Post([FromBody]dynamic value) {
       var x = value.var1.Value; // JToken
   }
   

2. Read just like Request.RequestUri.ParseQueryString()[key]

   public async Task Post() {        
      dynamic obj = await Request.Content.ReadAsAsync<JObject>();
      var y = obj.var1;
   }
   

3. Same as #2, just not asynchronously (?) so you can use it in a helper method

   private T GetPostParam<T>(string key) {
       var p = Request.Content.ReadAsAsync<JObject>();
       return (T)Convert.ChangeType(p.Result[key], typeof(T)); // example conversion, could be null...
   }
   

Caveat -- expects media-type application/json in order to trigger JsonMediaTypeFormatter handling.