Wrapping Native Async functions with Task<T>

I'm attempting to write a c# wrapper around a third-party library written in native code for consumption in our apps, which are almost exclusively written in .NET, and I'm trying to remain faithful to the C# patterns. Almost all the calls in this library are asynchronous in nature, and it would seem appropriate to wrap all my async calls into Task<T> objects. Here's an oversimplified example of how the native library is structured:

delegate void MyCallback(string outputData);

class MyNativeLibrary
{
    public int RegisterCallback(MyCallback callback); // returns -1 on error
    public int RequestData(string inputData);         // returns -1 on error
}

Right now, I've provided my return values through event subscription, however I believe this would be a far better way to return my data:

class WrapperAroundNativeCode
{
    public async Task<string> RequestData(string inputData);
}

So far I've been unsuccessful in finding an appropriate way to implement this, and I'm reaching out to folks with more experience in working with Task<T> objects and the async/await pattern than I do.