Look at Request.QueryString
Example from MSDN help
[Visual Basic]
Dim loop1, loop2 As Integer
Dim arr1(), arr2() As String
Dim coll As NameValueCollection
' Load Form variables into NameValueCollection variable.
coll=Request.QueryString
' Get names of all keys into a string array.
arr1 = coll.AllKeys
For loop1 = 0 To arr1.GetUpperBound(0)
Response.Write("Key: " & Server.HtmlEncode(arr1(loop1)) & "<br>")
' Get all values under this key.
arr2 = coll.GetValues(loop1)
For loop2 = 0 To arr2.GetUpperBound(0)
Response.Write("Value " & CStr(loop2) & ": " &
Server.HtmlEncode(arr2(loop2)) & "<br><br>")
Next loop2
Next loop1
[C#]
int loop1, loop2;
// Load NameValueCollection object.
NameValueCollection coll=Request.QueryString;
// Get names of all keys into a string array.
String[] arr1 = coll.AllKeys;
for (loop1 = 0; loop1 < arr1.Length; loop1++)
{
Response.Write("Key: " + Server.HtmlEncode(arr1[loop1]) + "<br>");
String[] arr2 = coll.GetValues(arr1[loop1]);
for (loop2 = 0; loop2 < arr2.Length; loop2++)
{
Response.Write("Value " + loop2 + ": " +
Server.HtmlEncode(arr2[loop2]) + "<br>");
}
}