Hi, how to call window opener function? I tried in this way but I get error : window.opener is null... Please help.Private Sub btnOK_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnOK.ClickAddUserToGroup(cboGroupName.SelectedValue, lstMember.SelectedValue, cboGroupName.SelectedItem.Text)ClientScript.RegisterClientScriptBlock(Me.GetType, "CloseWindowScript", "window.opener.ListAllMembers();window.close();", True) End Sub