Here is a code sample of my test page.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="junk2.aspx.cs" Inherits="Testing.junk2" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<%--<%@ Register Src="~/CustomControls/Header.ascx" TagPrefix="uc1" TagName="Header" %>--%>
<!DOCTYPE html>
<
html
xmlns
=
"http://www.w3.org/1999/xhtml"
>
<
head
runat
=
"server"
>
<
title
></
title
>
</
head
>
<
body
>
<
form
id
=
"form1"
runat
=
"server"
>
<
div
>
<
telerik:RadScriptManager
runat
=
"server"
ID
=
"rsm"
> </
telerik:RadScriptManager
>
<
telerik:RadTextBox
runat
=
"server"
ID
=
"txtFriendly"
Width
=
"400px"
Skin
=
"Silk"
></
telerik:RadTextBox
>
<
asp:RequiredFieldValidator
runat
=
"server"
ID
=
"RequiredFieldValidator1"
ControlToValidate
=
"txtFriendly"
Display
=
"Dynamic"
ErrorMessage
=
" * required"
CssClass
=
" text-danger"
/>
<
telerik:RadTextBox
runat
=
"server"
ID
=
"txtSubject"
Width
=
"400px"
Skin
=
"Silk"
></
telerik:RadTextBox
>
<%-- <
asp:RequiredFieldValidator
runat
=
"server"
ID
=
"RequiredFieldValidator5"
ControlToValidate
=
"txtSubject"
Display
=
"Dynamic"
ErrorMessage
=
" * required"
CssClass
=
" text-danger"
/>
--%>
<
telerik:RadWindowManager
ID
=
"RadWindowManager1"
runat
=
"server"
>
</
telerik:RadWindowManager
>
<
asp:Button
runat
=
"server"
ID
=
"btntest"
OnClick
=
"btntest_Click"
Text
=
"test"
CausesValidation
=
"false"
/>
</
div
>
</
form
>
</
body
>
</
html
>
And the codebehind:
protected
void
btntest_Click(
object
sender, EventArgs e)
{
RadWindow newWindow =
new
RadWindow();
newWindow.NavigateUrl =
"http://www.google.com"
;
newWindow.VisibleOnPageLoad =
true
;
RadWindowManager1.Windows.Add(newWindow);
}
If I comment out either (or both) of the 2 RequiredFieldValidator's, the modal displays. It doesn't matter which one is commented.
If both are on the page, I get no modal dialog.
We are using v2016.3.1018.45