C# Sending UrlEndcoded Form Data

Question

Trying to send UrlEncoded form data in Post request :

        client.BaseAddress = new Uri("myURI");

        var formContent = new MultipartFormDataContent();
        formContent.Headers.ContentType.MediaType = "application/x-www-form-urlencoded";

        formContent.Add(new StringContent("password"), "grant_type");
        formContent.Add(new StringContent("someUser"), "username");
        formContent.Add(new StringContent("somePassword"), "password");
        HttpResponseMessage response = client.PostAsync("token", formContent).Result;

For some reason the request headers contain the following :

 somePassword
 --7e556624-1d60-4321-a4ee-a85f6ab601c6
 Content-Type: text/plain; charset=utf-8
 Content-Disposition: form-data; name=username

 someUser
 --7e556624-1d60-4321-a4ee-a85f6ab601c6
 Content-Type: text/plain; charset=utf-8
 Content-Disposition: form-data; name=password

etc...

The Guid I guess is a boundary. However since I used urlencode it should be a '?' boundary.

In fact, if I call my service with Postman, using the same parameters and application/x-www-form-urlencoded then the request headers contain :

app_profile=freelancer&username=someUser&password=SomePassword&grant_type=password

So how do I achieve this with C# ?

[EDIT]

I managed to make it work like this. However I'd like to understand what was wrong in the original code ?

 var values = new Dictionary<string, string>
        {              
            {"username", "someUser"},
            {"password", "somePassword"},
            {"grant_type", "password"},
        };

        var formContent = new StringContent(JsonConvert.SerializeObject(values), Encoding.UTF8, "application/json");
        HttpResponseMessage response = client.PostAsync("token", new FormUrlEncodedContent(values)).Result;

Pavel Shastov · Accepted Answer · 2020-02-17 10:29:32Z

1

Initially, you used MultipartFormDataContent.

This means that Request content type will be replaced with multipart/form-data; boundary={some randomly generated key}

and the request body will be split in chunks using this {some randomly generated key} each chunk will have its own content type.

multipart/form-data content type especially useful when sending files together with other form data.

In the edited example, you are using StringContent

answered Feb 17, 2020 at 10:29

Pavel Shastov

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1 Comment

Sam Over a year ago

Thanks for clarifying. It makes sense.

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