Registering part of a string?

Quick question, I was setting up a keycode to unlock a door, and I decided a pretty efficient way to do this would be:
Set functions for the 1-9 keys.
Every key prints an individual number to a string.
If that string = the password, unlock the door.

Is this even possible? If so, let me know how to do it, or point me to a tutorial. Any help would be appreciated, thanks guys!

 

It's just string appending...

Code (csharp):

1.  
2. private string _input;
3.  
4. void Key9Pressed()
5. {
6.     _input += "9";
7. }
8.  

Is there something specific you need help with?

 

Was just going to update this, I had a code error and was looking for a new outlook. Shouldn't have given up so quickly, appending strings will work just fine. Thank you

 

Code (CSharp):

1. if (Input.GetKeyDown(keycode.9) {
2. // do something here
3. }
4. if (Input.GetKeyDown(keycode.8) {
5. // do something here
6. }
7. if (Input.GetKeyDown(keycode.7) {
8. // do something here
9.  }

Id do it this way...