Android Question Create a file in storage

Hi there...congratulations for the program..i accidentally found previus week it and i am very happy
Now i would like to ask you something about a test apk i am "playing"
I create a file with

File.WriteString(File.DirRootExternal, "text1.txt", txtall.Text)

Click to expand...

but i want the creation be only one time,at the very first time only that the application run.
Is that possible?
I mean can be a command that runs only one time?
thanks a lot