public void Action()
{
var request = new Request();
var task = request.OperationAsync()
.ContinueWith(t => Callback(t, request));
}
public void Action2()
{
var request = new Request();
var task = request.OperationAsync();
Callback2(task, request);
}
public async Task Action()
{
var request = new Request();
var task = request.OperationAsync();
await Callback(task, request);
}