How to create AsyncTask in Xamarin Android?

//here is code for AsyncTask perform long running background operation in Android.  

public class BackGroundTask : AsyncTask
{ 

private ProgressDialog _progressDialog;


public BackGroundTask(Context context)
{
_context = context;  

}

protected override void OnPreExecute()
{
base.OnPreExecute();

_progressDialog = ProgressDialog.Show(_context, " Progressing", "Please wait...");
}

protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)

{

}

protected override void OnPostExecute(Java.Lang.Object result)
{
base.OnPostExecute(result);  
_progressDialog.Hide();

}

How to launch Facebook app through Xamarin Android ?

here if facebook is not installed on your divice then it will redirect to web browser.

public void getFacebook(){

bool result=isAppInstalled("com.facebook.katana");

if(result)

{  

string v = FB_URL.Replace("https", "fb");  

var uri = Android.Net.Uri.Parse (v);

var intent = new Intent (Intent.ActionView, uri); 

StartActivity(intent);    

}

          else

{

StartActivity(new Intent(Intent.ActionView, Android.Net.Uri.Parse(FB_URL)));    

}

}

protected bool isAppInstalled(string packageName) 

{

Intent mIntent = PackageManager.GetLaunchIntentForPackage(packageName);

if (mIntent != null) 

{

return true;

}

else 

{

return false;

}

}

How to move cursor right side in edit text android ?

// this code will help you to move

private mEditext;
int cursorPos =mEditext.getSelectionStart();
cursorPos--;
if (cursorPos<0) cursorPos=0;
mEditext.setSelection(cursorPos);

How to send Email with Attachment Android

// put this code on your on button click

   final Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND);
   emailIntent.setType("plain/text");
   emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL, new String[]{"wadghanednyaneshwar@gmail.com"});
   emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, "Attachment");
   emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file:///mnt/sdcard/example.txt"));
   emailIntent.putExtra(android.content.Intent.EXTRA_TEXT, "gmail.com");

   MainActivity.this.startActivity(Intent.createChooser(emailIntent, "Send mail..."));