I am using Windows Forms .NET Framework and HTTPClient for web requests. I'm able so successfully get the response message. I'm now wanting to grab a specific attribute named 'special-price' from the 'item' elements. I only care about the first instance of a 'price-attribute' in an element. The following is a snippet of the code that is returning the error.
HttpResponseMessage request = await client.GetAsync($"url");
string result = request.Content.ReadAsStringAsync().Result;
XDocument xDocument = XDocument.Parse(result);
var query = from item in xDocument.Element("inv-balance").Elements("item")
select item.Attribute("special-price");
var answer = query.First();
rtxtResult.Text = answer.ToString();`
The error I keep getting is 'Object reference not set to an instance of an object'. I'm still relatively new to C# and this is the first major roadblock that I haven't been able to get past. Thank you.
Related
I'm just trying to use a Http POST method in a Blazor app through
public async Task CreateUnit(UnitEntity unit)
{
await _http.PostJsonAsync<UnitEntity>("api/units", unit);
}
_http and myObject have been defined elsewhere, but I'm getting this weird error. Can anyone help? This is the closest thing I could find elsewhere: https://github.com/dotnet/runtime/issues/30945.
The full error message is
System.Text.Json.JsonException: The input does not contain any JSON tokens. Expected the input to start with a valid JSON token, when isFinalBlock is true. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
And it here's the stack
Another reason this error could pop up, as it did for me, is simply because the API endpoint doesn't exist because it was misspelled.
I got a similar error in Program.cs Main method CreateHostBuilder(args).Build();:
System.FormatException: 'Could not parse the JSON file.'
JsonReaderException: The input does not contain any JSON tokens.
Expected the input to start with a valid JSON token, when isFinalBlock
is true. LineNumber: 0 | BytePositionInLine: 0.
For me it turned out to be the local secrets.json file that not contained a valid json object.
https://learn.microsoft.com/en-us/aspnet/core/security/app-secrets?view=aspnetcore-5.0&tabs=windows#secret-manager
Because of this I could not see any errors in Git or rollback to a working commit since the file is not checked in.
Solved by adding an empty object to the file via Visual Studio - right click the project in solution explorer and select Manage User Secrets:
{
}
https://learn.microsoft.com/en-us/aspnet/core/security/app-secrets?view=aspnetcore-5.0&tabs=windows#manage-user-secrets-with-visual-studio
In my case the code was doing this:
var json = await response.Content.ReadAsStringAsync();
var result = JsonObject.Parse(json); // threw the exception mentioned in the question
Why did that happen? That's because json value was an empty string "". Parse fails with an empty string.
Fixed it doing this simple change:
var json = await response.Content.ReadAsStringAsync();
var result = string.IsNullOrEmpty(json) ? null : JsonObject.Parse(json);
i had similar issue and the problem to check if the json string you are readying is empty, null, or bad formatted. debug to the code line where you are reading data into string before deserialize or serialize call.
I got this error when communicating between two APIs.
request = await req.DeserializeRequestBodyAsync<MyDto>(jsonSerializerOptions);
Turned out the code below did not actually send any values:
httpRequestMessage.Content = JsonContent.Create(myDto);
var httpClient = _clientFactory.CreateClient();
var httpResponseMessage = await httpClient.SendAsync(httpRequestMessage, cancellationToken);
I had to manually specify:
await httpRequestMessage.Content.LoadIntoBufferAsync();
Like this:
httpRequestMessage.Content = JsonContent.Create(myDto);
await httpRequestMessage.Content.LoadIntoBufferAsync();
var httpClient = _clientFactory.CreateClient();
var httpResponseMessage = await httpClient.SendAsync(httpRequestMessage, cancellationToken);
For me, this error occurred when calling FindByNameAsync of UserManager.
Sounds silly, but the database connection string in the appsettings was wrong!
Late answer - but I ran into this using Blazor WebAssembly with Browser Link (trying to get Hot Reload to work). Turns out it's an issue loading the appsettings and Browser Link was expecting the secrets file. I fixed by right clicking the Server project and copy/pasting my appsettings values into the secrets file.
In my case, I was passing the id of my object along with the object itself in the url of the put request to an API and faced the same exception. It turned out that it was not necessary to pass the id (as it was retrieved from the object itself, in fact it was not present in the method signature). Removing the id solved the problem.
This error occurred when communicating between client and web API.
API code:
public async Task<IActionResult> PostAsync(object review)
{
return Ok();
}
Client code:
var res = await _client.PostAsJsonAsync("api/reviews", review);
if (res.IsSuccessStatusCode)
{
var myObject = await res.Content.ReadFromJsonAsync<MyObject>(); //this line threw mentioned error
}
Turned out that the API endpoint was returning something different compared to what I was trying to read from JSON i.e. I was trying to read MyObject but API was returning ActionResult
In my case database column was marked not null and I was passing null in API.
I'm using Amazon API to generate request for ItemLookup. After signing the request I got a url:
http://webservices.amazon.com/onca/xml?AWSAccessKeyId=[AccessKey]&AssociateTag=[AssociateTag]&ItemId=B06XBCY6DW&Operation=ItemLookup&ResponseGroup=Images%2CItemAttributes%2COffers%2CReviews&Service=AWSECommerceService&Timestamp=2050-02-13T12:00:00Z&Version=2016-02-12&Signature=[Signature]
Which I use in browser and I can see nice xml with item's data, but When I try to get that data with c# I get error
The Uri parameter must be a file system relative or absolute path.
The method I'm using to get data is:
var itemXml = XElement.Load(url);
How can I get that xml in c#??
This is nothing .net core specific.
XElement.Load accepts a string - which, if you look at the intellisense states:
Loads an XElement from a file.
This isn't what you want. It's trying to resolve the URI from the filesystem.
You'll need to read the URL content into a Stream.
Try the following
var httpClient = new HttpClient();
var result = httpClient.GetAsync(url).Result;
var stream = result.Content.ReadAsStreamAsync().Result;
var itemXml = XElement.Load(stream);
Note I've used .Result - I would recommend instead using await (async/await) pattern
I am trying to use the new TFS/VSTS REST APIs with our on-prem TFS 2015 server, and cannot retrieve test runs as the response fails internal validation.
Using client code like the following:
var connection = new VssConnection(serverUri), credentials);
var client = connection.GetClient<TestManagementHttpClient>();
var runs = await client.GetTestRunsAsync("project", planId:183110);
throws a JsonSerializationException in line 3 with the following message:
Required property 'environmentName' not found in JSON. Pathvalue[0].testEnvironment', line 1, position 582.
which is accurate. Checking the response in Fiddler shows that the testEnvironment property only has an environmentId property, no name. I have uploaded a trimmed sample of the response to this gist.
My question is why does TFS not return this value or alternatively, is there a way to force the API SDK to ignore this validation error?
I can reproduce that issue if includeRunDetails parameter is true. I reported a bug here that you can vote it.
The workaround is that you could set includeRunDetails to false to get test runs without details include, then base on the result (test run id) to get a test run with details that you want.
client.GetTestRunByIdAsync
The lack of documentation on this subject coupled with the fact that I'm struggling with a learning curve on all fronts and making me really confused about where to start. I need to get this done using C# if possible. I apologize for the vagueness of this question, but I'm really lost. I would love links to comprehensive guides/references.
In my efforts to get this done, I've run into the following problems/questions:
I've created a web service using the otrs gui, with the operation CreateTicket, but requests via C# to my chosen namespace are returning 404 (not found). When I try to add a service reference or web reference with that namespace, I get the same error. However, when I plug that namespace into my browser as the url, it displays "customer.pl".
Can I send a soap request without adding the web service as a service reference in visual studio? Given the previous problem I'm having I can't do it that way. Would I just build the soap request string and write it to the web request's data stream with http://domain/rpc.pl as the uri?
If the answer to the previous question is yes... When trying the below code segment I get an internal server error (500) on the last line. However the header looks like a SOAP header which confuses me because I wouldn't have thought it got that far.
var document = new StringBuilder();
document.Append("<UserLogin>some user login</UserLogin>");
document.Append("<Password>some password</Password> ");
document.Append("<Ticket>");
document.Append("<Title>some title</Title> ");
document.Append("<CustomerUser>some customer user login</CustomerUser>");
document.Append("<Queue>some queue</Queue>");
document.Append("<State>some state</State>");
document.Append("<Priority>some priority</Priority>");
document.Append("</Ticket>");
document.Append("<Article>");
document.Append("<Subject>some subject</Subject>");
document.Append("<Body>some body</Body>");
document.Append("<ContentType>text/plain; charset=utf8</ContentType>");
document.Append("</Article>");
//var uri = new Uri("http://domain/injest");
var uri = new Uri("http://domain/rpc.pl");
var httpWebReq = (HttpWebRequest)WebRequest.Create(uri);
var bytePostData = Encoding.UTF8.GetBytes(document.ToString());
httpWebReq.Timeout = 5 * 1000;
httpWebReq.Method = "POST";
httpWebReq.ContentLength = bytePostData.Length;
httpWebReq.ContentType = "text/xml;charset=utf-8";
//httpWebReq.TransferEncoding=
//httpWebReq.ContentType = "application/xml";
//httpWebReq.Accept = "application/xml";
var dataStream = httpWebReq.GetRequestStream();
dataStream.Write(bytePostData, 0, bytePostData.Length);
dataStream.Close();
var httpWebResponse = (HttpWebResponse)httpWebReq.GetResponse();
Even if all you can offer is where to start, it would help me to know how to proceed, as I'm stumped.
You're using the rpc.pl endpoint which is part of the 'old' RPC-style interface.
You mention you added the web service via the GUI which means you're using the 'new' Generic Interface, which is indeed much easier from .Net.
The address of the endpoint is /otrs/nph-genericinterface.pl/Webservice/GenericTicketConnector or whatever you have called the web service in the admin section.
I am trying to call google maps geocode and am following the example on their webpage to try and apply it to mine
http://code.google.com/apis/maps/documentation/geocoding/index.html
in this example, the Geocoding API requests an xml response for the
identical query shown above for "1600 Amphitheatre Parkway, Mountain
View, CA":
http://maps.googleapis.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false
The XML returned by this request is shown below.
Now i am trying to run that url like this in my c# winforms application
string url = "http://maps.googleapis.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false";
WebRequest req = HttpWebRequest.Create(url);
WebResponse res = req.GetResponse();
StreamReader sr = new StreamReader(res.GetResponseStream());
try
{
Match coord = Regex.Match(sr.ReadToEnd(), "<coordinates>.*</coordinates>");
var b = coord.Value.Substring(13, coord.Length - 27);
}
finally
{
sr.Close();
}
However it doesnt seem to be returning anything and as such my var b line gives an index out of bounds error. Can anyone point me in the right direction for at least getting the example to work so i can apply the logic to my own application?
Thanks
If you visit your link "http://maps.googleapis.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false" directly in a browser you can see what it's returning. It's giving me a REQUEST DENIED error.
The problem is caused by the sensor=true_or_false parameter. You have to choose if you want it to be true or false. Google put it this way in their example so that you have to explicitly decide for yourself. This setting indicates if your application is using a location sensor or not. In your case, I'm guessing not, so set it to false.
If you change the link you're using to http://maps.googleapis.com/maps/api/geocode/xml?address=1600%20Amphitheatre%20Parkway,%20Mountain%20View,%20CA&sensor=false, I think you'll get the results you were expecting.