Add user and group in sharepoint

private void AddGroupAndUsers()
        { 
            SPWeb web = SPContext.Current.Web;
            web.AllowUnsafeUpdates = true;
            web.SiteGroups.Add("MyTestGroup", web.CurrentUser, web.CurrentUser, string.Empty);

            //Then you probably want to give some permissions to group (let’s try to provide contributor role)

            SPGroup group = web.SiteGroups["MyTestGroup"];
            SPRoleDefinition roleDefinition = web.RoleDefinitions.GetByType(SPRoleType.Contributor);
            SPRoleAssignment roleAssigment = new SPRoleAssignment(group);
            roleAssigment.RoleDefinitionBindings.Add(roleDefinition);
            web.RoleAssignments.Add(roleAssigment);
            web.Update();

           // Now you can add some users to your new group:

            SPUser spUser = web.EnsureUser("server\\username");
            group.Users.Add(spUser.LoginName, spUser.Email, spUser.Name, spUser.Notes);
            web.AllowUnsafeUpdates = false;