Stop ObjectDataSource From Data Binding When Validation Failed?

I have an ObjectDataSource that is bound to a GridView. The object accepts a parameter from a TextBox. The problem I have is when I use a CustomerValidator with a ServerValidate event, the ObjectDataSource would still attempt to perform a DataBind despite the fact the the customer validator has returned false. The following is the code in the ASPX page.

<asp:TextBox ID="sittingDate" runat="server" />
<asp:CustomValidator ID="DateValidator" runat="server" ControlToValidate="sittingDate" OnServerValidate="DateValidator_ServerValidate" />
<asp:ObjectDataSource ID="BatchDataSource" runat="server" OldValuesParameterFormatString="original_{0}"
SelectMethod="GetOrCreateSittingBatch" TypeName="BatchBLL" OnSelected="BatchDataSource_Selected" OnSelecting="BatchDataSource_Selecting">
<SelectParameters>
<asp:ControlParameter ControlID="sittingDate" Name="batchDate" PropertyName="Text"
Type="DateTime" />
</SelectParameters>
</asp:ObjectDataSource>
<asp:GridView ID="BatchGridView" runat="server" DataSourceID="BatchDataSource">

In the Custom Validator I have

protected void DateValidator_ServerValidate(object source, ServerValidateEventArgs args)
{
/Ensure that the entered data is a date.
string input = args.Value;
DateTime result;
args.IsValid = DateTime.TryParse(input.TrimEnd(), out result);
}

How do I stop the ObjectDataSource from data binding when validation has failed?