No cache with HttpClient in Windows Phone 8

Question

I've read that in order to disable caching while using get and post methods in `HttpClient`, I need to use a `WebRequestHandler` as my `HttpClient`'s `HttpClientHandler`, and change its cache policy. However, `WebRequestHandler` is not within System.Net.Http.dll, but rather in System.Net.Http.WebRequest.dll, so I tried to add the .dll to the project as a reference. I got an error message: Microsoft Visual Studio A reference to a higher version or incompatible assembly cannot be added to the project. Again, after a little search, I concluded that the .dll file was blocked because it was downloaded from another source. To unblock it, I went on trying the solution here. However, it didn't work either and I'm still getting the same error when I try to add the .dll file as a reference. All I want to do is disable caching using my HttpClient, am I doing anything wrong here? I'm open to any type of advice or help. My system is Windows 8.1 and I'm using Visual Studio 2013. The project I'm wor…

Accepted Answer

It's not possible to reference regular .NET assemblies in a Windows Phone 8 project. You can only use the .NET API for Windows Phone. This is a subset of regular .NET. See http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj207211%28v=vs.105%29.aspx for more info.

The default caching of HttpClient (and HttpWebRequest) can be worked around by appending a value to the query string. For example, a guid.

```
string uri = "http://host/path?cache=" + Guid.NewGuid().ToString();
```

A better solution, like pointed out in the comment above, is to set the "If-Modified-Since" header. HttpWebRequest has it built in:

```
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
if (request.Headers == null)
    request.Headers = new WebHeaderCollection();
// Make sure that you format time string according RFC.
// Otherwise setting header value will give ArgumentException for culture like 'ti-ER'
request.Headers[HttpRequestHeader.IfModifiedSince] = DateTime.UtcNow.ToString("r"); 
```

But you could add the header manually using an HttpClient I guess.

No cache with HttpClient in Windows Phone 8

Solution

Problem