public Task AddXapAsync(string relativeUri)
{
XapDownloadOperation operation;
if (_xapDownloadOperations.TryGetValue(relativeUri, out operation) && !operation.Task.IsFaulted)
return operation.Task;
operation = _xapDownloadOperations[relativeUri] = new XapDownloadOperation(relativeUri, this);
return operation.Task;
}
}