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();

}