Platform Invoke Sample - Changing the Desktop Wallpaper

private void button2_Click(object sender, System.EventArgs e)
{
int nResult ;
if (File.Exists(textBox1.Text))
{
nResult = AC.SystemParametersInfo(20, 0, textBox1.Text, 0x1 | 0x2 );
MessageBox.Show("Wallpaper has been changed");
}
}

Code : Modify the wallpaper.

Complete Code Listing

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.IO;
namespace WallPaper
{
public class WinAPI
{
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int SystemParametersInfo (int uAction , int uParam , string lpvParam , int fuWinIni) ;
}
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox textBox1;
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Button button2;
private System.Windows.Forms.OpenFileDialog openFileDialog1;
public Form1()
{
this.textBox1 = new System.Windows.Forms.TextBox();
this.button1 = new System.Windows.Forms.Button();
this.button2 = new System.Windows.Forms.Button();
this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
this.SuspendLayout();
this.textBox1.Location = new System.Drawing.Point(16, 16);
this.textBox1.Name = "textBox1";
this.textBox1.TabIndex = 0;
this.textBox1.Text = "";
this.button1.Location = new System.Drawing.Point(120, 16);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(24, 23);
this.button1.TabIndex = 1;
this.button1.Text = "...";
this.button1.Click += new System.EventHandler(this.button1_Click);
this.button2.Location = new System.Drawing.Point(16, 48);
this.button2.Name = "button2";
this.button2.Size = new System.Drawing.Size(128, 23);
this.button2.TabIndex = 2;
this.button2.Text = "Change Wallpaper";
this.button2.Click += new System.EventHandler(this.button2_Click);
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(232, 93);
this.Controls.AddRange(new System.Windows.Forms.Control[] {
this.button2,
this.button1,
this.textBox1});
this.Name = "Form1";
this.Text = "Change Desktop Wallpaper";
this.ResumeLayout(false);
}
protected override void Dispose( bool disposing )
{
base.Dispose( disposing );
}
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private void button1_Click(object sender, System.EventArgs e)
{
//change the initial directory if required.
openFileDialog1.InitialDirectory = @"C:\winnt";
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
textBox1.Text = openFileDialog1.FileName;
}
}
private void button2_Click(object sender, System.EventArgs e)
{
int nResult ;
if (File.Exists(textBox1.Text))
{
nResult = WinAPI.SystemParametersInfo(20, 0, textBox1.Text, 0x1 | 0x2 );
MessageBox.Show("Wallpaper has been changed");
}
}
}
}

NOTE: This article is purely for demonstration. This article should not be construed as a best practices white paper. This article is entirely original, unless specified. Any resemblance to other material is an un-intentional coincidence and should not be misconstrued as malicious, slanderous, or any anything else hereof.

Conclusion

In this example we learnt how to invoke Windows API functions using Platform Invoke. Many of the Windows API functions have corresponding implementation in the .Net framework namespaces and it is recommended to use the managed functions wherever possible.