public class BaseUserControl : UserControl
{
public BaseUserControl()
{
// automatically register the event
this.Load += new EventHandler(BaseUserControl_Load);
}

void BaseUserControl_Load(object sender, EventArgs e)
{
// something!
AssignValidationGroupToControls();
}

// assign the validation group to the controls
protected void AssignValidationGroupToControls()
{
// get the validation control from this control and assign the validation group
foreach (Control control in this.Controls)
{
PropertyInfo property = control.GetType().GetProperty("ValidationGroup");
if (property == null) continue;

property.SetValue(control, ValidationGroup, null);
}
}

public string ValidationGroup
{
get { return (string)ViewState["ValidationGroup"]; }
set { ViewState["ValidationGroup"] = value; }
}
}