Error saving txt file on external Storage MOBILE PHONE

OK dear Tuhin Paul,

Android Version: 9;

Language used: C# in XAMARIN

i use this code:

                string fileName = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, "Test.txt");

                //Pass the filepath and filename to the StreamWriter Constructor
                StreamWriter sw = new StreamWriter(fileName);
                //Write a line of text
                sw.WriteLine("Hello World!!");
                //Write a second line of text
                sw.WriteLine("From the StreamWriter class");
                //Close the file
                sw.Close();

I'll need more information to provide the better instructions:

1. Android Version and Development Environment:

• Which version of Android are you targeting (e.g., Android 13, 12, 11)?
• Are you using Kotlin or Java? Sharing your code for context would be helpful.

2. Permission Handling:

• Have you added the necessary permission to access external storage in your AndroidManifest.xml file? This is mandatory for Android 10 and later

I don't understand, 

please, I need write on external STORAGE on android mobile phone using XAMARIN

THANKS

Your trying to get path from Android.OS.Environment Change to iOS path