Generally when we upload any file using FileUpload Control and if their is TextBox with TextChange Event ,When TextChange Event fires the file from FileUpload Control will looses file due to postback,, on PostBack PostedFile property gets initilized with HttpPostedFile
object for the file. As we know that http request can't maintain state,
and PostedFile is initilized with HttpPostedFile Object so it loose it's
state.
By using State Managment Techniques we maintain File in FileUpload Control.
Lets Design one Page with FileUpload Control,Label, TextBox and Button.