Question

I’m working on a project where I need to extend WebClient for a custom implementation, MyWebClient.

I also need to make sure that MyWebClient is the only version that’s implemented by any developer on the project and no one uses the base WebClient class.

Is it possible to prevent the usage of WebClient, considering it’s not code that I have access to?

Answer 1

Depending on the features of WebClient you need, you could consider implementing MyWebClient as proxy that exposes only the methods you allow to be used from a WebClient member.

Example:

public class MyWebClient
{
    private WebClient HiddenWebClient {get; set;}

    // proxy sample
    public void DownloadFile(string address, string fileName)
    {
        HiddenWebClient.DownloadFile(address, fileName);
    }

   // other proxy methods & your specific implementation come here.

}

After, you will need a dedicated ctor and a maybe a factory to instantiate MyWebClient properly.

This won’t prevent your developers from using WebClient which would be far too difficult (see @gdoron suggestion, for instance), but will help avoiding its usage by mistake.

Edit:

From your last comment, I think that all you need is a Factory that will set the User Agent for all your WebClient instances.

Then, depending on your organization, you will need a strong communication about its usage (and maybe a search tool to look for new WebClient() in your projects).

public static class WebClientFactory
{
    public static WebClient Create()
    {
        WebClient result = new WebClient();
        result.Headers.Add("My Fancy User Agent");
        return result;
    }
}