Simple way to validate a Sharepoint 2010 pepoleeidtor control by required filed validator.

<SharePoint:PeopleEditor ID=”peBuyerName” runat=”server” AllowEmpty=”false” MultiSelect=”false”
ValidatorEnabled=”true” Width=”250px” SelectionSet=”User,SPGroup” ShowCreateButtonInActiveDirectoryAccountCreationMode=”true” />

: here is the validator
<asp:RequiredFieldValidator EnableClientScript=”true” ID=”RequiredFieldValidator1″
runat=”server” ControlToValidate=”peBuyerName” ErrorMessage=”Please enter a valid buyer name!”
ToolTip=”” ValidationGroup=”btnsubmit”></asp:RequiredFieldValidator>

……………enjoy