BUG: The icon that represents your form appears as a blank form icon in Visual C# .NET if you set the ShowInTaskBar property to False (836673)

WORKAROUND

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;
namespace WindowsApplication1
{
	/// <summary>
	/// Summary description for Form1.
	/// </summary>
	public class Form1 : System.Windows.Forms.Form
	{
		/// <summary>
		/// Required designer variable.
		/// </summary>
		private System.ComponentModel.Container components = null;
		public Form1()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

			//
			// TODO: Add any constructor code after InitializeComponent call
			//
		}
		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}
		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1));
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
			this.ClientSize = new System.Drawing.Size(292, 266);
			this.Icon = ((System.Drawing.Icon)(resources.GetObject("$this.Icon")));
			this.Name = "Form1";
			this.ShowInTaskbar = false;
			this.Text = "Form1";
			this.Load += new System.EventHandler(this.Form1_Load);
		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]

		static void Main() 
		{
			Application.Run(new Form1());
		}
		[DllImport("user32.dll")] 
		private static extern int SendMessage(IntPtr hwnd, int message, int wParam, IntPtr lParam); 
		[DllImport("user32.dll", ExactSpelling=true)] 
		private static extern IntPtr GetWindow(IntPtr hwnd, int cmd); 
		private IntPtr GetTopLevelOwner(Control c) 
		{
			IntPtr hwndOwner = c.Handle; 
			IntPtr hwndCurrent = c.Handle; 
			while (hwndCurrent != (IntPtr)0) 
			{
				hwndCurrent = GetWindow(hwndCurrent, GW_OWNER); 
				if (hwndCurrent != (IntPtr)0) { hwndOwner = hwndCurrent; } 
			} 
			return hwndOwner;
                } 
		private const int WM_SETICON = 0x80; 
		private const int GW_OWNER = 4; 
		private const int ICON_SMALL = 0; 
		private const int ICON_BIG = 1; 
		private void Form1_Load(object sender, System.EventArgs e) 
		{
			SendMessage(GetTopLevelOwner(this), WM_SETICON, ICON_BIG, this.Icon.Handle); 
                } 
		private void Form1_Closed(object sender, System.EventArgs e) 
		{ 
			SendMessage(GetTopLevelOwner(this), WM_SETICON, ICON_BIG, new IntPtr(0));
		}
	} 
}