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How to create file on android using xamarin?

I've tried several folders but looks like no file is created.
External read & write permission have been enabled.
The code run without any sign of error. (as given below)
Here is the screenshot of the code inside mainactivity.cs (this is for testing purposes).
I also assume that since this is platform specific, the code must be in android project.
string filename = Path.Combine(Xamarin.Essentials.FileSystem.AppDataDirectory, "count1.txt") ;
StreamWriter sw = File.CreateText(filename);
sw.WriteLine("asad ini test");
sw.Close();enter code here
1b. I 'm using Android 6.0 phone, but I can't find such folder /data/user...
(I'm not sure if such folder is targeted special version of Android)
I search both internal /Android/myproject/files/ and found nothing
I search external SDcard /Android/myproject/files/ and still found nothing
(please look at the my android phone folders, i can't even find /data folder
Once, this is accomplished the next step would be how to call this function from the generalproject (non android, non IOS, non UWP project).
Example to write file given in xamarin document.
Where should this code reside? in general project folder ? or, android project folder?

The term "external" used in android is very misleading. It doesn't mean the external removable SD card rather some folders that don't require "root" permission. Therefore, initially I can't find the folder which I save a file into.
Another reason is each phone manufacture uses different name, hence it is very difficult to get an absolute address of an external removable SD Card.
More details is explained in blog_external_removable_SD_Card
You can't write to the removable SD Card
an old post here

Android app says folder exists but I cant see it

I have an app I made on my old phone. It creates a folder called LocationTracker. When Im stepping through the code it says the folder exists. But I cant seem to browse to it when I connect my phone to the computer. I just checked my file explorer on my phone and i can browse to the folder there as well. According to that it is under the sd card, but i just cant see it on my PC.
Im rooting around in my file explorer on my phone. There appears to be 2 sd card folders. One is called sdcard1, and that seems to be my actual sd card. The other is called sd card. I think its an emulated one. I use Environment.getExternalStorageDirectory(), i thought that returned the sd card if one was available. If that is the case why is it using the emulated folder instead of the actual sd card folder? How do I fix this?

From Android documentation:
In devices with multiple "external" storage directories, this directory represents the "primary" external storage that the user will interact with. Access to secondary storage is available through
The rest of the sentence is sadly missing. However the methods are Context.getExternalFilesDirs() and Context.getExternalMediaDirs().

how to find exact path of android external storage programatically at runtime?

mySound.load(new URLRequest("file://mnt/sdcard/AnyFolder/YourSound.mp3"));`<br/>
I want to detect the name of the sdcard at runtime, so i can store my app-data on external storage.
The above codeline is an example of storing a mp3 to user's required location.

Maybe you are asking for:
File f = new File(Environment.getExternalStorageDirectory() +
"/" + "yourfilename");
I also recomend you to avoid writing to the root of the SD card. It is a good practice to write your aplication data into the appropriate folder:
File f = new File(Environment.getExternalStorageDirectory() +
"/Android/data/com.example.testapp/" + "yourfilename");
Obviously, you have to change the "com.example.testapp" with your app package (the package you entered when you created the project in Eclipse/Android Studio).

getExternalStorageDirectory()
in
http://developer.android.com/reference/android/os/Environment.html

use Environment.getExternalStorageState() it will give path to internal SD mount point like "/mnt/sdcard"

First, on Android 4.4+, you do not have write access to removable media (e.g., "external SD"), except for any locations on that media that might be returned by
getExternalFilesDirs() and getExternalCacheDirs().
See Dave Smith's excellent analysis of this, particularly if you want the low-level details.
Second, lest anyone quibble on whether or not removable media access is otherwise part of the Android SDK, here is Dianne Hackborn's assessment:
...keep in mind: until Android 4.4, the official Android platform has not supported SD cards at all except for two special cases: the old school storage layout where external storage is an SD card (which is still supported by the platform today), and a small feature added to Android 3.0 where it would scan additional SD cards and add them to the media provider and give apps read-only access to their files (which is also still supported in the platform today).
Android 4.4 is the first release of the platform that has actually
allowed applications to use SD cards for storage. Any access to them
prior to that was through private, unsupported APIs. We now have a
quite rich API in the platform that allows applications to make use of
SD cards in a supported way, in better ways than they have been able
to before: they can make free use of their app-specific storage area
without requiring any permissions in the app, and can access any other
files on the SD card as long as they go through the file picker, again
without needing any special permissions.

Where is android application installed in my sd card

I just want to view the files(especially the .png files) associated with one of the application in my mobile. The application is actually installed(moved) in the SD card.
The issue is ..I could not find the application in the SD card. I am using a file browser called 'File Manager' to browse through the SD card. Can someone help me on this.

It should be here:
/mnt/sdcard/Android/data/your_package_name/

Some hardware implements the path to the external storage different.
/mnt/sdcard/Android/data/your_package_name/
/mnt/sdcard-ext/Android/data/your_package_name/
You may be able to get a better view of what is on the device by using the ADB Shell. If you still have trouble at this point trying running grep or find from the shell.
UPDATE
Most of the time the files associates with your application are in the directory with your application. The application is installed in /data/data/your.package.name/. However you will need root access to get here if you are on a phone, I think the emulator lets you get here. As far as external storage... yea its a pain, to much fragmentation in the market. You have to programmatically check the location of the external storage.

On my device with Android 2.3.6 apps moved on the SD card are located into a directory named .android_secure as .asec files (see http://www.fileinfo.com/extension/asec).
They are not visible from the standard "Archive" browser which shows the hidden directory as empty.
The files are also encrypted so I guess no access to the images within is possible.

How to make a file hidden in android sd card?

I am creating android application which contains DB that needs to be hidden(not able to access by the user)in the SD Card. Can anyone tell me how to do this?

Any file stored on the SD card is accessible both by applications running on the phone, and by users who have mounted the SD card (both while it's in the phone and otherwise).
You can change the file properties to make it 'hidden', but it will still be easily found. There is no way to make a file on a public partition like an SD Card 'secure' in the manner you describe - users will always be able to copy, delete, and potentially change the file.
The best solution to your problem is to look into ways to encrypt your database to record it securely. You won't be able to prevent users from deleting or copying the file, but you should be able to make it difficult for them to read data from it or modify its contents.

For an easy solution, just prefix the db file with a . (like .dbfile). This will hide the file on Linux based systems, including android.
I am assuming that you want to hide the file to prevent users from accidentally deleting/changing it.

SD cards cannot be secured in the fashion you seek.

just name the file start by ."Dot"... ".myFolder/.myfile"

You can create a folder whose name starts with a dot(.) example (.dbfiles) android See these folders as configuration folder and do not show content of these folder in applications like gallery,music player...You can see these folders with advance file explorer like Es File explorer

Sdcard you cant't! Internal app data partition is the place for you.