I am new to the world of WPF - so not sure how to do the below functionality. It will be great if someone can help me.

I have developed an app using WPF (XAML). What I am trying to do is during the start up time of the app, I am trying to read a file (.txt and xml) and I am trying to load the content for the controls from there. Those names will overwrite the default names for the controls given in the xaml files. I am loading the default names in xaml file from a resx file.
For example, one control is the name of the. In resx file, I stored "default user". Now every user should be able to display there name by simple adding a pre-defined tag "My_Name" and then providing there name in a .txt file. The app, on strat up, should load that string from the .txt file.
I found out a way to do it in the code - by reading the string from the file and assiging thet Control.Content = "Name_Read_From_File" - but I am trying to do it at the strat-up time by parsing the xaml file directly - so that I can restrict the functionality in one place. Many thanks in advance...