The namespace 'MapPath' does not exist in the namespace

I am trying to use the code below to gather information from website and give the detail in HTML file. will I am trying to run the code I get error that

Error 41 The type or namespace name 'MapPath' does not exist in the namespace 'Microsoft.SqlServer.Server' (are you missing an assembly reference?)

the code is

WebRequest request = WebRequest.Create("http://www.google.com/");// url here
using (WebResponse response = request.GetResponse())
{
     using (StreamReader responseReader = new StreamReader(response.GetResponseStream()))
     {
         string responseData = responseReader.ReadToEnd();
         string path = Microsoft.SqlServer.Server.MapPath(".");
         if (!File.Exists(path + "//Asptrick.html"))
              File.Create(path + "//Asptrick.html");
         using (StreamWriter writer = new StreamWriter(path + "//Asptrick.html")) //Where You Want to save Content
         {
              writer.Write(responseData);
         }
     }
}

i have tried with

Server.MapPath("~")
Server.MapPath(@"\")
Server.MapPath("/")

but can not get it to work

the following are in used as well

using System.Net;
using System.IO;