Creating Facebook Event in C# Returns #100 Invalid Parameter

Question

I'm trying to put together a small app that will allow me to create events in Facebook. I've already got my Facebook app set up and have successfully tested a post to my feed through the application using the code below.

wc.UploadString("https://graph.facebook.com/me/feed", "access_token=" + AccessToken + "&message=" + Message);

When I try to take things to the next step, I've just hit a brick wall.

The code that I've written is here:

JavaScriptSerializer ser = new JavaScriptSerializer();
wc.UploadString("https://graph.facebook.com/me/events?" + "access_token=" + AccessToken, ser.Serialize(rawevent));

rawevent is a small object I wrote that puts together the elements of an event so I can pass it around my application. I'm using a similar method using ser.Deserialize to parse the user data coming back from Facebook, so I believe this should work the other way too.

Setting the above code aside for a moment, I also have tried simply putting plain text in there in various formats and with differing levels of parameters, and nothing seems to work.

Is there something wrong with the way I'm approaching this? I've read over everything I could get my hands on, and very few of the samples out there that I could find deal with creating events, and when they do, they're not in C#.

I would appreciate any help on this. If you even just have a clean copy of JSON code that I can look at and see where mine should be tweaked I would appreciate it.

I have included a copy of what the ser.Serialize(rawevent) call produces below:

{"name":"Dev party!","start_time":"1308360696.86778","end_time":"1310952696.86778","location":"my house!"}

EDIT:

thanks to bronsoja below, I used the code below to successfully post an event to Facebook!

            System.Collections.Specialized.NameValueCollection nvctest = new System.Collections.Specialized.NameValueCollection();
            nvctest.Add("name", "test");
            nvctest.Add("start_time", "1272718027");
            nvctest.Add("end_time", "1272718027");
            nvctest.Add("location", "myhouse");
            wc.UploadValues("https://graph.facebook.com/me/events?" + "access_token=" + AccessToken, nvctest);

Answer 1

All the posting examples in the graph api examples in FB docs show using curl -F, which indicates values be POSTed as normal form data. Just key value pair like you did in your first example.

The error is likely due to sending JSON. If you are using WebClient you may be able to simply create a NameValueCollection with your data and use WebClient.UploadValues to send the request.

Answer 2

I've recently found that Facebook returns (#100) Invalid parameter when we are trying to post data when there is already a record on file with the same name. So for example, if you are creating a FriendList via the API, and the name is "foo", submitting another identical request for the same name will immediately return that error.

In testing events you probably deleted the "Dev party!" event after each test, or maybe changing the time since you don't want two events to collide. But I'm wondering if you duplicated your wc.UploadValues(...) statement just as a test if you would see that error again. You're either deleting your 'test' event or maybe changing names and didn't notice that two events with the same name might return the error.

What's really bad here is that the error comes back as a OAuthException, which seems very wrong. This isn't a matter of authentication or authorization, it's purely a data issue.

Facebook Engineers, if I'm right about how this works, it's a bug to return this error under these conditions, and this forum has many examples of related confusion. Please return more appropriate errors.