/// <summary>
/// struct类型的IDisposable，如果给另外一个赋值了，在另一个对象无用之后，需要手动Dispose
/// </summary>
private void assignment()
{
DisposableStruct temp = d;
temp.id = id++;
temp.Dispose(); // **
}
private void RefReturn(ref DisposableStruct info)
{
DisposableStruct temp = info;
temp.id = id++;
info.Dispose();
info = new DisposableStruct(id++);
temp.Dispose();
}
