UWP C# Opening a text file in Notepad.

Hello @VoyTec ,
Welcome to Microsoft Q&A!

You can refer to the document Launch the default app for a file to select the file opening method to select Notepad to open the txt file.

async void DefaultLaunch()  
{  
   // Path to the file in the app package to launch  
      string imageFile = @"images\test.png";  
        
   var file = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync(imageFile);  
  
   if (file != null)  
   {  
      // Set the option to show the picker  
      var options = new Windows.System.LauncherOptions();  
      options.DisplayApplicationPicker = true;  
  
      // Launch the retrieved file  
      bool success = await Windows.System.Launcher.LaunchFileAsync(file, options);  
      if (success)  
      {  
         // File launched  
      }  
      else  
      {  
         // File launch failed  
      }  
   }  
   else  
   {  
      // Could not find file  
   }  
}  

Thank you.
Junjie

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