REST – Bruce Ng's software development blog

Web service failed to read query string parameter correctly

For certain characters when putting in query string parameters they need to be URL encoded or they will cause problem to the web service.

I faced this problem with the # character, encoding it and use %23 instead solved the problem.

Firefox requests for XML format when performing a GET to Web API

Today while testing the Ext JS application I was writing on various browsers, something strange happened. The app works on IE and Chrome, while on Firefox it breaks.

It turns out if not configured correctly WebAPI will return data depending on the Accept HTTP header sent by browsers, and different browsers sent different HTTP Accept header.

More details in the SO answer: http://stackoverflow.com/a/31934984

Firefox prefers XML, so Web API try to serialize data in XML format to return to Firefox.

IE and Chrome doesn’t prefer one over other, so Web API chooses Json.

I solved this issue in Firefox by configuring the web api to always return JSON by adding the following line to WebApiConfig.cs

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue(“text/html”));

Using Ext JS proxy ajax writer

The default behaviour of Ext JS proxy ajax writer seems to be to always use POST. Whenever trying to create/update/delete a record, a JSON object will be sent to the server in the request payload through POST.

It might be possible to configure the proxy and writer to use other HTTP methods like PUT and DELETE, but I haven’t seen any documentation on this yet.

The Id field is always included. So there are 3 cases

When the request is to create/update the record, the fields with data will be included. Example: {“Id”:1, “Name”:”Tom”}. Using the Id the server can determine whether it’s a update or create request if a record with same Id already exists.
When deleting a record, only the Id is included in the JSON object. Example: {“Id”: 1}. The server can determine that it’s a delete request by checking the number of properties the JSON object has.

If the server is written in ASP.NET Web API, it’s important to read the request body and process it manually instead of using a parameter in the method and let the framework do the deserialization automatically, because then it will not be possible to count the number of properties the object original has, the deserialized object has all properties with default values for missing ones.