If you want to set the ControlToValidate property of an ASP.NET validator to the DateTimeControl’s ID, it will throw an error!
As you can guess, you have to target the controls inside the DateTimeControl.

Since the DateTimeControl set the name of the controls programmatically, you can retrieve the id of the control:

• Textbox date: DateTimeControl.ID +”Date”
• Dropdownlist hours: DateTimeControl.ID +”DateHours”
• Dropdownlist minutes: DateTimeControl.ID +”DateMinutes”

Example:

If you use the SharePoint:DateTimeControl with the TimeOnly property set to “true”

<SharePoint:DateTimeControl runat="server" ID="TheTime" TimeOnly="true"/>

You’ll have two dropdownlists, one for the hours and one for the minutes
The DateTimeControl set the name:

Dropdownlist hours: DateTimeControl.ID +”DateHours”

Html will be:

<select name="ctl00$PlaceHolderMain$ctl07$ctl02$TheTime$TheTimeDateHours" id="ctl00_PlaceHolderMain_ctl07_ctl02_TheTime_TheTimeDateHours" dir="ltr">
 <option value="00:">00:</option>
 <option value="01:">01:</option>
 <option value="02:">02:</option>
 <option value="03:">03:</option>
 <option value="04:">04:</option>
 <option value="05:">05:</option>
 <option value="06:">06:</option>
 <option value="07:">07:</option>
 <option value="08:">08:</option>
 <option value="09:">09:</option>
 <option value="10:">10:</option>
 <option value="11:">11:</option>
 <option value="12:">12:</option>
 <option value="13:">13:</option>
 <option value="14:">14:</option>
 <option value="15:">15:</option>
 <option value="16:">16:</option>
 <option value="17:">17:</option>
 <option value="18:">18:</option>
 <option value="19:">19:</option>
 <option value="20:">20:</option>
 <option value="21:">21:</option>
 <option value="22:">22:</option>
 <option value="23:">23:</option>
</select>

Dropdownlist minutes: DateTimeControl.ID +”DateMinutes”
Html will be:

<select name="ctl00$PlaceHolderMain$ctl07$ctl02$TheTime$TheTimeDateMinutes" id="ctl00_PlaceHolderMain_ctl07_ctl02_TheTime_TheTimeDateMinutes" dir="ltr">
 <option value="00">00</option>
 <option value="05">05</option>
 <option value="10">10</option>
 <option value="15">15</option>
 <option value="20">20</option>
 <option value="25">25</option>
 <option value="30">30</option>
 <option value="35">35</option>
 <option value="40">40</option>
 <option value="45">45</option>
 <option value="50">50</option>
 <option value="55">55</option>
</select>

So you can retrieve the ASP.NET controls by using :

• For the date: TheTime$TheTimeDate
• For the hours: TheTime$TheTimeDateHours
• For the minutes: TheTime$TheTimeDateMinutes

Real case example:

I have two DateTimeControl, one named TheStartTime and one other named TheEndTime,

I want to validate that the end time is not before the start time.

So I’ll use the ASP.NET comparevalidator validator to compare the hours:

<asp:CompareValidator id="valDate" runat="server" ControlToValidate="TheEndTime$TheEndTimeDateHours" ControlToCompare="TheStartTime$TheStartTimeDateHours"
 Type="Integer"
 Operator="GreaterThanEqual"
 ErrorMessage="The end time must be greater than the start time">
 </asp:CompareValidator >

Now, if you want to validate both hours and minutes, one option is to add an “asp:CustomValidator” and check conditions server side :
Markup:

<asp:CustomValidator runat="server" ID="EndTimeMustBeLaterThanStartTimeCustomValidator"
EnableClientScript="false" ErrorMessage="Start time must be before end time"/>

Before the action, validate:

if (!IsEndTimeLaterThanStartTime())
{
 EndTimeMustBeLaterThanStartTimeCustomValidator.IsValid = false;
 return;
}

Validation method:

private bool IsEndTimeLaterThanStartTime()
{
 // retrieve the DropDownList
 DropDownList startHours = TheStartTime.FindControl("TheStartTimeDateHours") as DropDownList;
 DropDownList endHours = TheEndTime.FindControl("TheEndTimeDateHours") as DropDownList;

 // prevent from errors
 if (startHours == null ||
 endHours == null ||
 string.IsNullOrEmpty(startHours.SelectedValue) ||
 string.IsNullOrEmpty(endHours.SelectedValue))
 {
 return; // dont' do anything
 }

// the hour value is "00:"
 int startHour = Convert.ToInt32(startHours.SelectedValue.Replace(":",""));
 int endHour = Convert.ToInt32(endHours.SelectedValue.Replace(":", ""));
 if (endHour < startHour)
 {
 args.IsValid = false;
 }
 else
 {

 if (endHour == startHour)
 {
 // check the minutes
 DropDownList startMinutes = TheStartTime.FindControl("TheStartTimeDateMinutes") as DropDownList;
 DropDownList endMinutes = TheEndTime.FindControl("TheEndTimeDateMinutes") as DropDownList;
 // prevent from errors
 if (startMinutes == null ||
 endMinutes == null ||
 string.IsNullOrEmpty(startMinutes.SelectedValue) ||
 string.IsNullOrEmpty(endMinutes.SelectedValue))
 {
 return; // dont' do anything
 }

 int startMinute = Convert.ToInt32(startMinutes.SelectedValue);
 int endMinute = Convert.ToInt32(endMinutes.SelectedValue);

 if (endHour <= startMinute)
 args.IsValid = false;

 }
 }

 args.IsValid = true;

 }

You can also validate the Date himself if you choose to display it,
you can make a client side validation if you know javascript,
you can do everything like in “classic” ASP.NET.

my extension method

public static SPFolder GetParentFolder(this SPListItem spListItem)

{

if (spListItem == null)

return null;

SPFile spFile = spListItem.Web.GetFile(spListItem.Url);

if (spFile == null)

return null;

return spFile.ParentFolder;

}

Use

SPFolder parentFolder = sPListItem.GetParentFolder();

if (parentFolder != null)

{

// do some stuffs..

}