ContactSelectorDialogViewModel.cs

using System;
using System.Collections.Generic;
using Prism.Dialogs;
using PrismSample.Models;
using PrismSample.Services;

namespace PrismSample.ViewModels
{
    public class ContactSelectorDialogViewModel : BaseViewModel, IDialogAware
    {
        private readonly IContactsService _contactsService;

        public ContactSelectorDialogViewModel(IContactsService contactsService)
        {
            _contactsService = contactsService;
        }

        // note: acting upon search query is not implemented
        private string _query;
        public string Query
        {
            get => _query;
            set => SetProperty(ref _query, value);
        }

        private List<Contact> _contacts;
        public List<Contact> Contacts
        {
            get => _contacts;
            set => SetProperty(ref _contacts, value);
        }

        private Contact _selectedContact;
        public Contact SelectedContact
        {
            get => _selectedContact;
            set => SetProperty(ref _selectedContact, value, onChanged:OnContactSelected);
        }

        private void OnContactSelected()
        {
            if(SelectedContact != null)
                RequestClose(new DialogParameters {{"Contact", SelectedContact}});
        }

        public async void OnDialogOpened(IDialogParameters parameters)
        {
            Contacts = await _contactsService.GetContacts();
        }

        public bool CanCloseDialog() => true;
        public void OnDialogClosed() { }
        public event Action<IDialogParameters> RequestClose;
    }
}