VirtualPathUtility class from MSDN

 1 protected void Page_Load(object sender, EventArgs e)
 2 {
 3    StringBuilder sb = new StringBuilder();
 4    String pathstring = Context.Request.FilePath.ToString();
 5    sb.Append("Current file path = " + pathstring + "<br>");
 6    sb.Append("File name = " + VirtualPathUtility.GetFileName(pathstring).ToString() + "<br>");
 7    sb.Append("File extension = " + VirtualPathUtility.GetExtension(pathstring).ToString() + "<br>");
 8    sb.Append("Directory = " + VirtualPathUtility.GetDirectory(pathstring).ToString() + "<br>");
 9    Response.Write(sb.ToString());
10     
11    StringBuilder sb2 = new StringBuilder();
12    String pathstring1 = Context.Request.CurrentExecutionFilePath.ToString();
13    sb2.Append("Current Executing File Path = " + pathstring1.ToString() + "<br>");
14    sb2.Append("Is Absolute = " + VirtualPathUtility.IsAbsolute(pathstring1).ToString() + "<br>");
15    sb2.Append("Is AppRelative = " + VirtualPathUtility.IsAppRelative(pathstring1).ToString() + "<br>");
16    sb2.Append("Make AppRelative = " + VirtualPathUtility.ToAppRelative(pathstring1).ToString() + "<br>");
17    Response.Write(sb2.ToString());
18 }