Webservices object reference not set to an instance of an object error - json

Question

I have to make a call to the web service (JSON) to authenticate the user who is trying to login to the app. I have the following xml provided
<summary>
http://geniewebsvc.cloudapp.net/Member.svc/Authenticate
</summary>
<param name="payload">
{"UserName":"testuser#somedomain.com","Password":"p#$$w0rd"}
</param>
<requiredHeaders>
Content-Type: application/json;charset=UTF-8
</requiredHeaders>
<returns></returns>
[OperationContract]
[WebInvoke(UriTemplate = "/Authenticate", Method = "POST", ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare)]
AuthenticateResponse Authenticate(AuthCredentials usernamePassword);
There is similar one to check if the userid is already registered and that is a Get method. That works fine and i receive the right response for both successful and unsuccessful cases. But all the post methods are the ones which are giving me trouble. and i noticed that there is one more difference in these xmls.. i.e., the .. the isregistered webservice param tag goes something like this..
<param name="emailAddress"></param>
and here is my get() and post() please let me know whats my mistake...
public void Post()
{
RequestState myRequestState = new RequestState();
try
{
System.Uri uri = new Uri(url);
HttpWebRequest myHttpWebGetRequest;
Logger.log(TAG, "Create a HttpWebrequest object to the URL", url);
myHttpWebGetRequest = (HttpWebRequest)WebRequest.Create(uri);
_mHttpWebRequest = myHttpWebGetRequest;
myRequestState.conn = this;
myRequestState.request = myHttpWebGetRequest;
myRequestState.request.ContentType = "application/json;charset=UTF-8";
myRequestState.request.Method = "POST";
myRequestState.request.AllowReadStreamBuffering = false;
myRequestState.request.Headers["UserName"] = "rick.labarbera#gmail.com";
myRequestState.request.Headers["Password"] = "125124514";
// myRequestState.request.Headers["MemberId"] = "UdE8IwmTbxEjmzmMo2nBpg==";
IAsyncResult result = (IAsyncResult)myHttpWebGetRequest.BeginGetResponse(new AsyncCallback(RespCallback), myRequestState);
}
catch (Exception e)
{
close(myRequestState);
if (this.listener != null)
{
Logger.log(TAG, "post()", e.Message);
}
}
}
public void Get()
{
RequestState myRequestState = new RequestState();
try
{
System.Uri uri = new Uri(url);
HttpWebRequest myHttpWebPostRequest;
Logger.log(TAG, "Create a HttpWebrequest object to the URL", url);
myHttpWebPostRequest = (HttpWebRequest)WebRequest.Create(uri);
_mHttpWebRequest = myHttpWebPostRequest;
myRequestState.conn = this;
myRequestState.request = myHttpWebPostRequest;
myRequestState.request.Method = "GET";
myRequestState.request.AllowReadStreamBuffering = false;
IAsyncResult result = (IAsyncResult)myHttpWebPostRequest.BeginGetResponse(new AsyncCallback(RespCallback), myRequestState);
}
catch (Exception e)
{
close(myRequestState);
if (this.listener != null)
{
Logger.log(TAG, "get()", e.Message);
}
}
}
Am i doing something wrong???All these things are very very new to me.. I need help badly..
Thanks :)

Answer 1

I have played a bit with your code, but couldn't make it :(
What are the URL's you are using for the POST() method and for GET() methods.?
By the way, There is another way around to invoke your service. Follow these steps:
-- Create a new project.
-- Right-click on the Project name and click on "Add Service Reference"... Then provide address as "http://geniewebsvc.cloudapp.net/Member.svc" and click Go.
-- Once service information is downloaded, provide Namespace something like "MyMemberService" and click Ok.
Then Goto your MainPage.xaml.cs and write the following code.
MemberServiceClient client = new MemberServiceClient();
client.AuthenticateCompleted += new EventHandler<AuthenticateCompletedEventArgs>(client_AuthenticateCompleted);
client.AuthenticateAsync(new AuthCredentials() { UserName = "rick.labarbera#gmail.com", Password = "125124514" });
And the AuthenticateCompleted handler is
void client_AuthenticateCompleted(object sender, AuthenticateCompletedEventArgs e)
{
MessageBox.Show(e.Result.Successful.ToString());
}
This way you can simply call any service in the MemberService with just 2 or 3 lines of code. This is how a soap client is invoked in a Visual Studio project.
But again, there are some "Endpoint configuration" issues in this which you need to solve. And if you can do that you can save atleast 30 to 40 % of your development time.
Good luck.