compareValidator Compare to textboxes with dates - asp.net

Question

My compare validator is firing always even if it is greater and even if it is less.
<tr>
<td>
Selection Start Date:
</td>
<td>
<asp:TextBox ID="SelectionStartDateTextBox" runat="server"
Text='<%# Bind("SelectionStartDate") %>'></asp:TextBox>
<asp:RequiredFieldValidator runat="server" ID="RequFilesStart"
ControlToValidate="SelectionStartDateTextBox"
ErrorMessage="Enter Selection Start date!" ValidationGroup="validation1">
</asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
Selection End Date:
</td>
<td>
<asp:TextBox ID="SelectionEndDateTextBox" runat="server"
Text='<%# Bind("SelectionEndDate") %>'></asp:TextBox>
<asp:RequiredFieldValidator runat="server" ID="ReqFiledEnd"
ControlToValidate="SelectionEndDateTextBox"
ErrorMessage="Enter Selection End date!" ValidationGroup="validation1">
</asp:RequiredFieldValidator>
<asp:CompareValidator ID="CompareValSelDate" runat="server"
ControlToValidate="SelectionEndDateTextBox"
ControlToCompare="SelectionStartDateTextBox"
CultureInvariantValues="true" Type="Date"
Operator="LessThanEqual" ValidationGroup="validation1"
ErrorMessage="Selection End Date should be greater then Selected start date"
Display="dynamic">
</asp:CompareValidator>
</td>
</tr>
I also have set it up Culture="en-GB" and have also set it up same on my web config.
I am using Ajax toolkit to display calendar attached to the TextBox
<cc1:calendarextender id="Calendarextendera3" runat="server" format="dd MMM yyyy"
targetcontrolid="SelectionEndDateTextBox">
</cc1:calendarextender>
<cc1:calendarextender id="Calendarextendera4" runat="server" format="dd MMM yyyy"
targetcontrolid="SelectionStartDateTextBox">
</cc1:calendarextender>
Please help I dont know what to do.
Thanks in advance

Answer 1

You should set
CultureInvariantValues="false"
in your CompareValidator. Too, the date format should be that of your current culture.
The CompareValidator seems not to be able to compare the format dd MMM yyyy. If you want to display this format, you can use a custom validator to compare the dates:
<asp:CustomValidator runat="server" ID="datesValidator" OnServerValidate="DatesValidator_Validate" ErrorMessage="end date should be greater than or equal to start date"></asp:CustomValidator>
protected void DatesValidator_Validate(object source, ServerValidateEventArgs args)
{
DateTime startDate = Convert.ToDateTime(SelectionStartDateTextBox.Text);
DateTime endDate = Convert.ToDateTime(SelectionEndDateTextBox.Text);
if (endDate < startDate)
{
args.IsValid = false;
}
}