how to upload a document file in the text box

You cannot upload a file into a control, instead you upload a file into your server's file system, and from there you read the content of that file (if you know how the file is developed; like the basic underlying concepts) and then (as a string) you can add them to the TextBox. 


Anyhow, it depends on how you allow the user to upload the resume, which file formats you're working on and how you want to implement the TextBox control in your application.