Message box in UWP not working

Question

Please help me, I have ran into a problem. I'm new in UWP coding problem : I have build a simple application which consists of a button. When the button is pressed it will display a message

Error : Cannot find typre System.Collections.CollectionBase in module CommonLanguageRuntimeLibrary

Here is my code

using System;    
using System.Collections.Generic;   
using System.IO;   
using System.Linq;   
using System.Runtime.InteropServices.WindowsRuntime;  
using Windows.Foundation;  
using Windows.Foundation.Collections;  
using Windows.UI.Xaml;  
using Windows.UI.Xaml.Controls;  
using Windows.UI.Xaml.Controls.Primitives;  
using Windows.UI.Xaml.Data;  
using Windows.UI.Xaml.Input;  
using Windows.UI.Xaml.Media;  
using Windows.UI.Xaml.Navigation;  
using System.Windows.MessageBox;  
using System.Windows.Forms;  

// The Blank Page item template is documented at     https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace App1  
{   
/// <summary>   
/// An empty page that can be used on its own or navigated to within a Frame.   
/// </summary>   
public sealed partial class MainPage : Page  
{    
    public MainPage()   
    {    
        this.InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        MessageBox.Show("HI");
    }
}
}

Answer 1

There is no MessageBox in UWP but there is a MessageDialog :

using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.UI.Popups;
using System;

namespace App1
{
    /// <summary>   
    /// An empty page that can be used on its own or navigated to within a Frame.   
    /// </summary>   
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            var dialog = new MessageDialog("Hi!");
            await dialog.ShowAsync();
        }
    }
}

Answer 2

I strongly recommend you to use a separate, function to display a popup message.

UWP uses the namespace Windows.UI.Popups and not System.Windows.MessageBox , since it's only used for Win32 or WinForms applications

Here's a good way to display your desired message:

// Other namespaces (essential)
...

// Required namespaces for this process
using Windows.UI.Popups;
using System.Runtime.InteropServices;

namespace PopupMessageApp
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        // I will only comment those that are not obvious to comprehend.
        private async void ShowMessage(string title, string content, [Optional] object[][] buttons)
        {
            MessageDialog dialog = new MessageDialog(content, title);

            // Sets the default cancel and default indexes to zero. (incase no buttons are passed)
            dialog.CancelCommandIndex   = 0;
            dialog.DefaultCommandIndex  = 0;

            // If the optional buttons array is not empty or null.
            if (buttons != null)
            {
                // If there's multiple buttons
                if (buttons.Length > 1)
                {
                    // Loops through the given buttons array
                    for (Int32 i = 0; i < buttons.Length; i++)
                    {
                        /* Assigns text and handler variables from the current index subarray.
                         * The first object at the currentindex should be a string and 
                         * the second object should be a "UICommandInvokedHandler" 
                         */
                        string text = (string)buttons[i][0];

                        UICommandInvokedHandler handler = (UICommandInvokedHandler)buttons[i][1];

                        /* Checks whether both variables types actually are relevant and correct.
                         * If not, it will return and terminate this function and not display anything.
                         */
                        if (handler.GetType().Equals(typeof(UICommandInvokedHandler)) &&
                            text.GetType().Equals(typeof(string)))
                        {
                            /* Creates a new "UICommand" instance which is required for
                             * adding multiple buttons.
                             */
                            UICommand button = new UICommand(text, handler);

                            // Simply adds the newly created button to the dialog
                            dialog.Commands.Add(button);
                        }
                        else return;
                    }
                }
                else
                {
                    // Already described
                    string text = (string)buttons[0][0];

                    UICommandInvokedHandler handler = (UICommandInvokedHandler)buttons[0][1];

                    // Already described
                    if (handler.GetType().Equals(typeof(UICommandInvokedHandler)) &&
                        text.GetType().Equals(typeof(string)))
                    {
                        // Already described
                        UICommand button = new UICommand(text, handler);

                        // Already described
                        dialog.Commands.Add(button);
                    }
                    else return;
                }

                /* Sets the default command index to the length of the button array.
                 * The first, colored button will become the default button or index.
                 */
                dialog.DefaultCommandIndex = (UInt32)buttons.Length;
            }

            await dialog.ShowAsync();
        }

        private async void MainPage_Load(object sender, EventArgs e)
        {
            /* Single object arrays with a string object and a "UICommandInvokedHandler" handler.
             * The ShowMessage function will only use the first and second index of these arrays.
             * Replace the "return" statement with a function or whatever you desire.
             * (The "return" statemnet will just return and do nothing (obviously))
             */
            object[] button_one = { "Yes", new UICommandInvokedHandler((e) => { return; }) };
            object[] button_two = { "No", new UICommandInvokedHandler((e) => { return; }) };

            /* Object arrays within an object array.
             * The first index in this array will become the first button in the following message.
             * The first button will also get a different color and will become the default index.
             * For instance, if you press on the "enter" key, it will press on the first button.
             * You can add as many buttons as the "Windows.UI.Popups.MessageDialog" wants you to.
             */
            object[][] buttons = new object[][]
            {
                button_one,
                button_two
            };

            // Displays a popup message with multiple buttons
            ShowMessage("Title", "Content here", buttons);

            /* Displays a popup message without multiple buttons.
             * The last argument of the ShowMessage function is optional.
             * because of the definition of the namespace "System.Runtime.InteropServices".
             */
            ShowMessage("Title", "Content here");

            // PS, I have a life, just trying to get points xD // BluDay
        }
    }
}

This way, you can display a message dialog with or without passing an object array with subarrays that contains of buttons. This method is extremely efficient. If you like this, make sure you fully understand it!