dealing with zip files in c#

Question

i have a zip file .i copied that file directly into my solution explorer .i want to extract that file .my code is

public void UnZip()

{

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

System.IO.Directory.CreateDirectory("C:\\extractedFiles");

Shell32.Folder output = sc.NameSpace("C:\\extractedFiles");

Shell32.Folder input = sc.NameSpace("/51047839.zip");

output.CopyHere(input.Items(), 40);

}

private void button1_Click(object sender, EventArgs e)

{

UnZip();

 }

 

 

 but i got error: object is not found.set a reference.....  how can solve it