Retrieving Users from Subsite SharePoint Groups.

try
            {
                string strAllUsers = string.Empty;
                SPSecurity.RunWithElevatedPrivileges(delegate()
                {
                    strAllUsers += "<Table width='100%' cellpadding='0' cellspacing='0'>";
                    strAllUsers += "<Tr>";
                    strAllUsers += "<Td colspan='4' bgcolor='#add8e6'>";
                    strAllUsers += "</Td>";
                    strAllUsers += "</Tr>";
                    strAllUsers += "<Tr>";
                    strAllUsers += "<Td colspan='4' Align='Center'>";
                    strAllUsers += "<Strong>";
                    strAllUsers += "Subsites Users using this site";
                    strAllUsers += "</Strong>";
                    strAllUsers += "</Td>";
                    strAllUsers += "</Tr>";
                    strAllUsers += "<Tr>";
                    strAllUsers += "<Td bgcolor='#add8e6'>";
                    strAllUsers += "<Strong>";
                    strAllUsers += "UserName";
                    strAllUsers += "</Strong>";
                    strAllUsers += "</Td>";
                    strAllUsers += "<Td bgcolor='#add8e6' nowrap='nowrap'>";
                    strAllUsers += "<Strong>";
                    strAllUsers += "SharePoint Group";
                    strAllUsers += "</Strong>";
                    strAllUsers += "</Td>";
                    strAllUsers += "<Td bgcolor='#add8e6'>";
                    strAllUsers += "<Strong>";
                    strAllUsers += "EmailID";
                    strAllUsers += "</Strong>";
                    strAllUsers += "</Td>";
                    strAllUsers += "<Td bgcolor='#add8e6' nowrap='nowrap'>";
                    strAllUsers += "<Strong>";
                    strAllUsers += "SubWeb Name";
                    strAllUsers += "</Strong>";
                    strAllUsers += "</Td>";
                    strAllUsers += "</Tr>";
                    strAllUsers += "<Tr>";
                    strAllUsers += "<Td colspan='4' bgcolor='#add8e6'>";
                    strAllUsers += "</Td>";
                    strAllUsers += "</Tr>";
                    SPWeb currentWeb = SPContext.Current.Web;
                    foreach (SPWeb objWeb in currentWeb.GetSubwebsForCurrentUser())
                    {
                        foreach (SPGroup grp in objWeb.Groups)
                        {
                            foreach (SPUser user in grp.Users)
                            {
                                string strUser = string.Empty;
                                string strGroup = string.Empty;
                                string strUserEmail = string.Empty;
                                string strSubWebTitle = string.Empty;
                                string strSubWebUrl = string.Empty;
                                strUser = user.Name;
                                strGroup = grp.Name;
                                strUserEmail = user.Email;
                                strSubWebTitle = objWeb.Title;
                                strSubWebUrl = objWeb.Url;
                                strAllUsers += "<Tr>";
                                strAllUsers += "<Td>";
                                strAllUsers += strUser;
                                strAllUsers += "</Td>";
                                strAllUsers += "<Td>";
                                strAllUsers += strGroup;
                                strAllUsers += "</Td>";
                                strAllUsers += "<Td>";
                                strAllUsers += strUserEmail;
                                strAllUsers += "</Td>";
                                strAllUsers += "<Td>";
                                strAllUsers += "<a href='"+strSubWebUrl+"'>"+strSubWebTitle+"</a>";
                                strAllUsers += "</Td>";
                                strAllUsers += "</Tr>";
                                strAllUsers += "<Tr>";
                                strAllUsers += "<Td colspan='4' bgcolor='#add8e6'>";
                                strAllUsers += "</Td>";
                                strAllUsers += "</Tr>";
                            }
                        }
                    }
                    strAllUsers += "</Table>";
                    writer.Write(strAllUsers);
                });
            }
            catch (Exception ex)
            {
                writer.Write(ex.ToString());
            }