How can I implement both an async method and its synchronous counterpart? [duplicate]

Question

I have a method such as Task<string> GetContentAsync(string url) and my console application is not quite ready to take advantage of the TPL internally, but maybe at a later date it will be.

How can I easily write a synchronous wrapper (not an alternative implementation) for this (or other) methods?

Answer 1

If your library needs to implement both synchronous and asynchronous members, then you implement both members. There are no shortcuts (assuming this is intended to be a reusable library).

public async Task<string> GetContentAsync(string url)
{
  ... // Logic here, e.g., using HttpClient
}

public string GetContent(string url)
{
  ... // Duplicate logic here, e.g., using WebClient
}

The duplication of logic is certainly unfortunate, but if you try to take shortcuts you'll actually end up in a worse situation. The details of "why" are a bit long for an SO answer, but Stephen Toub covers the problems that arise when wrapping in his classic pair of blog posts "Should I expose synchronous wrappers for asynchronous methods?" and "Should I expose asynchronous wrappers for synchronous methods?"

BTW, the answer to both questions is "no". Also, see my SO answer here.