You could do something like:

private void button21_Click_1(object sender, EventArgs e)

{

   // Note: Add a ref to the Com dll 'Microsoft Shell Controls And
Automation' in your project.

   // Creates a new zip container and adds directory to it.

   string zipFile = @"c:\myzip.zip";

   if (!System.IO.File.Exists(zipFile))

       System.IO.File.Delete(zipFile);

   using(FileStream fs = new FileStream(zipFile, FileMode.Create,
FileAccess.Write))

   {

       byte[] emptyzip = new byte[] { 80, 75, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

       fs.Write(emptyzip, 0, emptyzip.Length);

   }

   //Copy a folder and all its contents into zip file.

   Shell32.ShellClass sc = new Shell32.ShellClass();

   Shell32.Folder SrcFlder = sc.NameSpace(@"C:\temp\sampleapp");

   Shell32.Folder DestFlder = sc.NameSpace(zipFile);

   Shell32.FolderItems items = SrcFlder.Items();

   DestFlder.CopyHere(items, 20);

   Console.WriteLine("Done.");

}