Using the all the Request.ServerVariables Object

Active Server Pages exposes an object called ServerVariables, which is part of the Request object. This ServerVariables object allows the programmer to see many environment variables. You can use the ServerVariables along with IIS's directory sercurity options to determine who is currently accessing your site. You can also grab the visitor's IP address using the ServerVariables object.

Method
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using System.Collections.Specialized;

protected void Button1_Click(object sender, EventArgs e)
{

NameValueCollection NVCSrvElements = Request.ServerVariables;
string[] array1 = NVCSrvElements.AllKeys;

for (int i = 0; i < array1.Length; i++)
{
Response.Write(array1[i] + "<br>");
}
}