C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Media;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Imaging;
using System.Windows.Threading;

namespace WpfMineSweeper
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        const int size = 25;
        const string mine = "bombe.jpg";
        const string flag = "flag.png";
        static readonly Random rnd = new Random();

        private List<Button> field;

        private List<Postion> positions;
        private DispatcherTimer timer;

        private int fieldWidth;
        private int fieldHeight;
        private int mines;
        public int LeftFlags => mines - positions.Count(a => a.HasFlag);
        private bool started = false;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void CreateField(int width, int height, int mines)
        {
            positions = new List<Postion>();
            canvas.Children.Clear();
            field = new List<Button>();

            fieldWidth = width;
            fieldHeight = height;
            this.mines = mines;
            canvas.Width = size * width;
            canvas.Height = size * height;
            for (int x = 0; x < width; x++)
            {
                for (int y = 0; y < height; y++)
                {
                    Button but = new Button()
                    {
                        Content = "",
                        Width = size,
                        Height = size,
                        Name = $"but_{x}_{y}",
                        FontWeight = FontWeights.Bold
                    };
                    positions.Add(new Postion() { X = x, Y = y });
                    but.PreviewMouseLeftButtonDown += But_PreviewMouseLeftButtonDown;
                    but.PreviewMouseRightButtonDown += But_PreviewMouseRightButtonDown;

                    Canvas.SetLeft(but, x * size);
                    Canvas.SetTop(but, y * size);

                    canvas.Children.Add(but);
                    field.Add(but);
                }
            }

            while (positions.Count(a => a.IsMine) < mines)
            {
                var temp = positions.Where(a => !a.IsMine);
                temp.ElementAt(rnd.Next(0, temp.Count())).IsMine = true;
            }
            for (int i = 0; i < positions.Count; i++)
            {
                Postion cur = positions[i];

                var temp = positions.Where(a => (Math.Abs(cur.X - a.X) == 1 && Math.Abs(cur.Y - a.Y) == 0)
                 || (Math.Abs(cur.X - a.X) == 0 && Math.Abs(cur.Y - a.Y) == 1)
                 || (Math.Abs(cur.X - a.X) == 1 && Math.Abs(cur.Y - a.Y) == 1));

                positions[i].Mines = temp.Count(a => a.IsMine);
            }

            textBlockFlagsLeft.Text = $"Verbleibende Flaggen: {LeftFlags}";
        }

        private void StartGame()
        {
            timer = new DispatcherTimer();
            DateTime startTime = DateTime.Now;
            timer.Tick += delegate { textBlockTime.Text = (DateTime.Now - startTime).ToString("h'h 'm'm 's's'"); };
            timer.Interval = new TimeSpan(0, 0, 1);

            int w, h, m;
            if (int.TryParse(textBoxWidth.Text, out w) && w > 0 && int.TryParse(textBoxHeight.Text, out h) && h > 0 && int.TryParse(textBoxMines.Text, out m) && m > 0 && m < w * h)
            {
                CreateField(w, h, m);
            }
            else
            {
                MessageBox.Show("Falsche Eingaben");
                return;
            }
            started = true;
            buttonStartStop.Content = "Beenden";
            textBlockTime.Text = (new TimeSpan()).ToString("h'h 'm'm 's's'");
            timer.Start();
        }

        private void EndGame()
        {
            timer.Stop();
            started = false;
            buttonStartStop.Content = "Starten";
        }

        private void ExplosionSound()
        {
            Task.Factory.StartNew(delegate
            {
                SoundPlayer player = new SoundPlayer(Properties.Resources.bombExplosion);
                player.Play();
            });
        }

        private void ShowMines()
        {
            foreach (Postion pos in positions)
            {
                Button button = field.Single(a => a.Name == $"but_{pos.X}_{pos.Y}");
                if(pos.IsMine)
                {
                    button.Content = GetImage(mine);
                }

                else
                {
                    button.Content = pos.Mines.ToString(); 
                }
            }
        }

        static Image GetImage(string file)
        {
            Image img = new Image();
            BitmapImage source = new BitmapImage();
            source.BeginInit();
            source.UriSource = new Uri(file, UriKind.Relative);
            source.EndInit();

            img.Source = source;

            return img;
        }

        private void buttonStartStop_Click(object sender, RoutedEventArgs e)
        {
            if (!started)
            {
                StartGame();
            }
            else
            {
                EndGame();
            }
        }

        private void But_PreviewMouseRightButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (started)
            {
                Button caller = (Button)sender;

                int x, y;
                var split = caller.Name.Split('_');
                x = int.Parse(split[1]);
                y = int.Parse(split[2]);

                var pos = positions.SingleOrDefault(a => a.X == x && a.Y == y);

                if (pos.HasFlag)
                {
                    pos.HasFlag = false;
                    caller.Content = null;
                }
                else if (!pos.HasFlag && LeftFlags > 0)
                {
                    pos.HasFlag = true;

                    caller.Content = GetImage(flag);

                    if (positions.Where(a => a.HasFlag && a.IsMine).Count() == mines)
                    {
                        EndGame();
                        MessageBox.Show("Du hast alle Minen gefunden. Das Spiel ist vorbei!");
                    }
                }

                textBlockFlagsLeft.Text = $"Verbleibende Flaggen: {LeftFlags}";
            }
        }

        private void But_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (started)
            {
                Button caller = (Button)sender;

                int x, y;
                var split = caller.Name.Split('_');
                x = int.Parse(split[1]);
                y = int.Parse(split[2]);

                var pos = positions.SingleOrDefault(a => a.X == x && a.Y == y);
                if (pos.HasFlag)
                {
                    pos.HasFlag = false;
                    textBlockFlagsLeft.Text = $"Verbleibende Flaggen: {LeftFlags}";
                }
                if (pos.IsMine)
                {
                    caller.Content = GetImage(mine);
                    EndGame();
                    ExplosionSound();
                    ShowMines();
                    MessageBox.Show("Du bist leider auf eine Mine getreten. Das Spiel ist vorbei!");
                }
                else
                {
                    caller.Content = pos.Mines;
                }
            }
        }
    }

    class Postion
    {
        public int X { get; set; }
        public int Y { get; set; }

        public bool IsMine { get; set; }
        public int Mines { get; set; }
        public bool HasFlag { get; set; }

        public override bool Equals(object obj)
        {
            Postion p = (Postion)obj;

            return X == p.X && Y == p.Y;
        }

        public override int GetHashCode()
        {
            int hash = 13;
            hash = (hash * 7) + X.GetHashCode();
            hash = (hash * 7) + Y.GetHashCode();
            return base.GetHashCode();
        }
    }
}

XML-Code

<Window x:Class="WpfMineSweeper.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfMineSweeper"
        mc:Ignorable="d"
        Title="MainWindow" Height="550" Width="725" x:Name="main">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="1*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Grid Margin="0,10,0,0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="1*"/>
            </Grid.ColumnDefinitions>
            <Grid Grid.Column="0">
                <TextBlock Text="Spielfeldbreite" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,3,0,0"/>
                <TextBox x:Name="textBoxWidth" Width="50" Text="10" TextAlignment="Center" Margin="91,0,0,0"/>
            </Grid>
            <Grid Grid.Column="1">
                <TextBlock Text="Spielfeldhöhe" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,3,0,0"/>
                <TextBox x:Name="textBoxHeight" Width="50" Text="10" TextAlignment="Center" Margin="86,0,0,0"/>
            </Grid>
            <Grid Grid.Column="2">
                <TextBlock Text="Minen" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,3,0,0"/>
                <TextBox x:Name="textBoxMines" Width="50" Text="10" TextAlignment="Center" Margin="49,0,0,0"/>
            </Grid>
            <Button x:Name="buttonStartStop" Content="Start" Grid.Column="3" HorizontalAlignment="Left" Margin="10,2,0,0" VerticalAlignment="Top" Width="75" Click="buttonStartStop_Click"/>
        </Grid>
        <ScrollViewer Grid.Row="1" Margin="10" ScrollViewer.VerticalScrollBarVisibility="Auto" ScrollViewer.HorizontalScrollBarVisibility="Auto"> 
            <Canvas x:Name="canvas" Background="LightGray"/>
        </ScrollViewer>
        <StackPanel Grid.Row="2" Orientation="Horizontal" Margin="10,0,10,0" Background="LightGray">
            <TextBlock x:Name="textBlockTime" Margin="10,10"/>
            <TextBlock x:Name="textBlockFlagsLeft" Margin="10,10"/>
        </StackPanel>
    </Grid>
</Window>