An alert box can be popped-up on a Xamarin.Forms Page by the method, DisplayAlert. We can provide a Title, Body (Text to be alerted) and one/two Action Buttons. Page offers two overrides of DisplayAlert method.

1. public Task DisplayAlert (String title, String message, String cancel)

This override presents an alert dialog to the application user with a single cancel button. The alert displays modally and once dismissed the user continues interacting with the application.

Example :

DisplayAlert ("Alert", "You have been alerted", "OK");

Above snippet will present a native implementation of Alerts in each platform (AlertDialog in Android, UIAlertView in iOS, MessageDialog in Windows) as below.

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1. public System.Threading.Tasks.Task<bool> DisplayAlert (String title, String message, String accept, String cancel)

This override presents an alert dialog to the application user with an accept and a cancel button. It captures a user's response by presenting two buttons and returning a boolean. To get a response from an alert, supply text for both buttons and await the method. After the user selects one of the options the answer will be returned to the code.

Example :

var answer = await DisplayAlert ("Question?", "Would you like to play a game", "Yes", "No");
Debug.WriteLine ("Answer: " + (answer?"Yes":"No"));

Example 2:(if Condition true or false check to alert proceed)

async void listSelected(object sender, SelectedItemChangedEventArgs e)
    {
        var ans = await DisplayAlert("Question?", "Would you like Delete", "Yes", "No");
        if (ans == true)
        {
            //Success condition
        }
        else
        {
            //false conditon
        }
     }

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var alertResult = await DisplayAlert("Alert Title", Alert Message, null, "OK");
if(!alertResult)
{
   //do your stuff.
}

Here we will get Ok click action.