The means of splash screen is a screen through which we can show the booting process of a thread. When you start your computer then first to load booting process after then load operating system. I will do the same thing in wpf. This screen appear before loading the start page. So lets to start it:


1. First to add a new window in the project.
2. Add these properties inside window tag.

 Title="SplashScreen"
 Height="300"
Width="300"
ResizeMode="NoResize"
WindowStyle="None"
WindowStartupLocation="CenterScreen"
Background="Green"
BorderThickness="8"
BorderBrush="Black"

3. Now, you complete code is:

<Window x:Class="SplashSCreen.SplashScreen"
        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:SplashSCreen"
        mc:Ignorable="d"
        Title="SplashScreen" Height="300" Width="300" ResizeMode="NoResize" WindowStyle="None" WindowStartupLocation="CenterScreen" Background="Green" BorderThickness="8" BorderBrush="Black">
 
4. Add a label control in the page with content, like

<Grid>
        <Label x:Name="label" Content="Data Uploading......." HorizontalAlignment="Left" Margin="37,128,0,0" VerticalAlignment="Top" Width="187"/>

    </Grid>

5. Now, add this code in the app.xaml.cs file 

App.xaml.cs file

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace SplashSCreen
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        private const int min_spl_time = 4000;
        protected override void OnStartup(StartupEventArgs e)
        {
            SplashScreen splash = new SplashScreen();
            splash.Show();
            Stopwatch timer = new Stopwatch();
            timer.Start();
            base.OnStartup(e);
            MainWindow main = new MainWindow();
            timer.Stop();
            int remaining_time = min_spl_time - (int)timer.ElapsedMilliseconds;
            if (remaining_time > 0)
                Thread.Sleep(remaining_time);
            splash.Close();
        }
    }
}
Here SplashScreen is the name of window or you can say class name.