I need to initialize the text attribute of the text box element with a property from some where else when actually I can simply do this from code but it will be much m
You can set the text on a page in a similar way.
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But in order for this to work, you will need to DataBind the control on Page_Load. For multiple TextBox controls you could just loop through each and databind them so that you do not have to hard code the databinding of each.
I am not sure what your ContextItem is though, so you would have to modify my code.