private void Add()
{
int y = 0;
string oldRepositoryIDs = string.Empty;
foreach (Repository s in repository)
{
oldRepositoryIDs += s.Id + "E";
}
do
{
y++;
}while (oldRepositoryIDs.Contains("R" + y.ToString() + "E"));
string repositoryID = "R" + y.ToString();
Repository newRepository = new Repository(repositoryID, "", "");
repository.Add(newRepository);
repository.OnContentChanged();
}