Warn Users before leaving a page with uncommitted changes

[Dan]

My users want the ability to receive a warning if they leave a page without hitting the save button.  I found some great code at 4GuysFromRolla, and have been able to make a necessary adjustment  to get it working with the RadComboBox.  I am struggling on finding the right change for the RadEditor.  What is the correct html element id to put in the following code?

'ASP.net article found here: http://www.4guysfromrolla.com/articles/042005-1.aspx
'Dont forget to register controls on the Page_load even.
'Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'    'Monitor the changes for the Web controls whose values you want to watch
'    MonitorChanges(InputControlname)
'    'For those controls (like "Save" buttons) that cause a postback that should NOT prompt the
'    'user, call BypassModifiedMethod
'    BypassModifiedMethod(btnSave)
'End Sub
Public Sub MonitorChanges(ByVal wc As WebControl)
    If wc Is Nothing Then Exit Sub
    If TypeOf wc Is CheckBoxList OrElse TypeOf wc Is RadioButtonList Then
        'Add an array element for each item in the checkbox/radiobutton list
        For i As Integer = 0 To CType(wc, ListControl).Items.Count - 1
            ClientScript.RegisterArrayDeclaration("monitorChangesIDs", """" & String.Concat(wc.ClientID, "_", i) & """")
            ClientScript.RegisterArrayDeclaration("monitorChangesValues", "null")
        Next
    ElseIf TypeOf wc Is Telerik.Web.UI.RadComboBox Then
        ClientScript.RegisterArrayDeclaration("monitorChangesIDs", """" & wc.ClientID & "_Input" & """")
        ClientScript.RegisterArrayDeclaration("monitorChangesValues", "null")
    ElseIf TypeOf wc Is Telerik.Web.UI.RadEditor Then
        'Not working.  Still need to find the correct ID Value.
        ClientScript.RegisterArrayDeclaration("monitorChangesIDs", """" & wc.ClientID & "ContentHiddenTextarea" & """")
        ClientScript.RegisterArrayDeclaration("monitorChangesValues", "null")
    Else
        ClientScript.RegisterArrayDeclaration("monitorChangesIDs", """" & wc.ClientID & """")
        ClientScript.RegisterArrayDeclaration("monitorChangesValues", "null")
    End If
    AssignMonitorChangeValuesOnPageLoad()
End Sub
Private Sub AssignMonitorChangeValuesOnPageLoad()
    If Not ClientScript.IsStartupScriptRegistered("monitorChangesAssignment") Then
        ClientScript.RegisterStartupScript(Me.GetType(), "monitorChangesAssignment", _
           "<script language=""JavaScript"">" & vbCrLf & _
           "  assignInitialValuesForMonitorChanges();" & vbCrLf & _
           "</script>")
        ClientScript.RegisterClientScriptBlock(Me.GetType(), "monitorChangesAssignmentFunction", _
           "<script language=""JavaScript"">" & vbCrLf & _
           "  function assignInitialValuesForMonitorChanges() {" & vbCrLf & _
           "    for (var i = 0; i < monitorChangesIDs.length; i++) {" & vbCrLf & _
           "      var elem = document.getElementById(monitorChangesIDs[i]);" & vbCrLf & _
           "      if (elem) if (elem.type == 'checkbox' || elem.type == 'radio') monitorChangesValues[i] = elem.checked; else monitorChangesValues[i] = elem.value;" & vbCrLf & _
           "    }" & vbCrLf & _
           "  }" & vbCrLf & vbCrLf & vbCrLf & _
           "  var needToConfirm = true;" & vbCrLf & _
           "  window.onbeforeunload = confirmClose;" & vbCrLf & vbCrLf & _
           "  function confirmClose() {" & vbCrLf & _
           "    if (!needToConfirm) return;" & vbCrLf & _
           "    for (var i = 0; i < monitorChangesValues.length; i++) {" & vbCrLf & _
           "      var elem = document.getElementById(monitorChangesIDs[i]);" & vbCrLf & _
           "      if (elem) if (((elem.type == 'checkbox' || elem.type == 'radio') && elem.checked != monitorChangesValues[i]) || (elem.type != 'checkbox' && elem.type != 'radio' && elem.value != monitorChangesValues[i])) { needToConfirm = false; setTimeout('resetFlag()', 750); return ""You have modified the data entry fields since last savings.  If you leave this page, any changes will be lost.  To save these changes, click Cancel to return to the page, and then Save the data.""; }" & vbCrLf & _
           "    }" & vbCrLf & _
           "  }" & vbCrLf & vbCrLf & _
           "  function resetFlag() { needToConfirm = true; } " & vbCrLf & _
           "</script>")
    End If
End Sub
Public Sub BypassModifiedMethod(ByVal wc As WebControl)
    wc.Attributes("onclick") = "javascript:" & GetBypassModifiedMethodScript()
End Sub
Public Function GetBypassModifiedMethodScript() As String
    Return "needToConfirm = false;"
End Function

Thanks for your help,
Dan Neuman

[Rumen]

Hi,

You can use the following code:

<telerik:RadEditor ID="RadEditor1" runat="server" OnClientLoad="OnClientLoad">
</telerik:RadEditor>
<script type="text/javascript">
    var contentChanged = false;

    function OnClientLoad(editor) {
        editor.attachEventHandler("keydown", function(sender, e) {
            contentChanged = true;
        });
    }

    window.onbeforeunload = unloadMessage;
    function unloadMessage() {
        message = "Content has changed, save before exit?"
        if (contentChanged)
            return message;

    }
</script>
<asp:Button ID="Button1" Text="text" runat="server" />

If the content is updated, the browser will ask the user whether she/he wants to proceed if the user tries to close the window or navigate to another page.

Greetings,
Rumen
the Telerik team

[Dan]

Thanks for the code.  I tweaked it a minor bit so the other controls on the page could take advantage of the comparison of values instead of a plan key being pressed, and everything works beautifully!