c# - OpenFileOutput does not exist in the current context -

i have 2 files trying same thing. first activity, , works:

[activity (label = "local files sample", mainlauncher = false)] public class activity1 : activity {     int count = 0;     static readonly string filename = "count";     string path;     string filename;       protected override async void oncreate (bundle bundle)     {         base.oncreate (bundle);          // set our view "main" layout resource         setcontentview (resource.layout.main2);          path = system.environment.getfolderpath (system.environment.specialfolder.personal);         filename = path.combine (path, filename);          task<int> loadcount = loadfileasync ();          console.writeline ("could excueted before load finished!");          // our button layout resource,         // , attach event         button button = findviewbyid<button> (resource.id.mybutton);         button btnsave = findviewbyid<button> (resource.id.btnsave);         button btnreset = findviewbyid<button> (resource.id.btnreset);         textview txtstored = findviewbyid<textview> (resource.id.stored);         textview txtpath = findviewbyid<textview> (resource.id.path);          button.click += delegate {             button.text = string.format ("{0} clicks!", ++count); };          btnsave.click += async delegate {              btnsave.text = string.format ("current count saved: {0}", count);             txtstored.text = string.format (this.getstring (resource.string.stored), count);             await writefileasync();         };          btnreset.click += delegate {             file.delete (filename);             btnsave.text = this.getstring (resource.string.save);             txtstored.text = string.format (this.getstring (resource.string.stored), 0);         };          count = await loadcount;         txtpath.text = filename;         txtstored.text = string.format (this.getstring (resource.string.stored), count);     }      async task<int> loadfileasync()     {          if (file.exists (filename)) {             using (var f = new streamreader (openfileinput (filename))) {                 string line;                 {                     line =await f.readlineasync();                 } while (!f.endofstream);                 console.writeline ("load finished");                 log.info ("---", "loaded=" + line);                 return int.parse (line);              }         }         return 0;     }      async task writefileasync()     {         using (var f = new streamwriter (openfileoutput (filename, filecreationmode.append | filecreationmode.worldreadable))) {             await f.writelineasync (count.tostring ()).configureawait(false);         }         console.writeline ("save finished!");         log.info ("---", "saved=" + count);     } } 

the second c# class, , doesn't work:

public class class_io {     int count = 0;     //static readonly string filename = "count";     string path;     string filename;      public class_io ()     {     }      async task<int> loadfileasync ()     {          if (file.exists (filename)) {             using (var f = new streamreader (openfileinput (filename))) {                 string line;                 {                     line = await f.readlineasync ();                 } while (!f.endofstream);                 console.writeline ("load finished");                 log.info ("---", "loaded=" + line);                 return int.parse (line);              }         }         return 0;     }      async task writefileasync ()     {         using (var f = new streamwriter (openfileoutput (filename, filecreationmode.append | filecreationmode.worldreadable))) {             await f.writelineasync (count.tostring ()).configureawait (false);         }         console.writeline ("save finished!");         log.info ("---", "saved=" + count);     } } 

why openfileinput not available in "the current context"? how make work?

openfileoutput method on context - in order work in generic class need pass in current context, or retrieve using android.app.application.context