c# - Invalid Operation Exception in file saving -

i have code , don't know why pops error message :

"invalid operation exception unhandled user code".

this error comes out when press save button.

the purpose of program save text 1 textbox in mytest.txt file , file textbox1. appreciate here. thank in advance.

    public mainpage()     {         this.initializecomponent();     }      private void buttonsave_click(object sender, routedeventargs e)     {         string path = @"c:\users\geora\mytest.txt";         if(!file.exists(path))         {             using (streamwriter sw = file.createtext(path))             {                 sw.writeline(textbox.text);             }         }     }      private void buttonshow_click(object sender, routedeventargs e)     {         string path = @"c:\users\geora\mytest.txt";         using (streamreader sr = file.opentext(path))         {             string s = "";             s = sr.readline();             textbox1.text = s;         }     } 

you have opened files not closed file.this might issue

streamreader sr = file.opentext(path) 

you need close it. using (and disposes it's gc'd sooner):

or alternatively in .net 2 can use new file. static members, don't need close anything:

variable = file.readalltext(path);