♣ コード

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

public class WebApplication : System.Web.UI.Page
{
    protected System.Web.UI.WebControls.Label Label1;

    public void Page_Load(object sender, EventArgs e)
    {
        this.Label1.Text = Request.UserAgent;
    }
}

♣ 実行例

    Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 1.1.4322; .NET CLR 1.0.3705)