Naming of WPF-Controls in Markup

As I stated in another post, I access at times controls direct from the code behind. If I do this I name the controls as I do also in ControlTemplates and DataTemplates, I give them the prefix PART_ and after that I precise the name, for example…

<TextBox Name=”PART_UserName” />

Is this against a common WPF naming scheme? Formerly I used the prefix m_ followed by the description…

<TextBox Name=”m_userName” />

.. because in reality its exactly this, but I don’t liked it. What do you think? Please note, I don’t want to discuss whether to use MVVM or not. There are situations I don’t care about.