C#

public class Tasks
{
	public static void ForceControlValidation(Control c)
	{
		Type t = typeof(Control);

		// validate:
		MethodInfo m = t.GetMethod("NotifyValidating", BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic);
		object obj = m.Invoke(c, new object[0]);

		// finish validating
		if (obj is bool && (bool)obj == false)
		{
			MethodInfo m2 = t.GetMethod("NotifyValidated", BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic);
			m2.Invoke(c, new object[0]);
		}
	}
}

public void ValidateFocusedControl()
{
    foreach(Control ctl in Controls)
        if(ValidateFocusedControlRecursive(ctl))
            break;
}

bool ValidateFocusedControlRecursive(Control ctl)
{
    if(ctl.Focused)
    {
        if(ctl.CausesValidation)
        {
            CancelEventArgs cea = new CancelEventArgs();
            cea.Cancel = false;

            ctl.Validating(ctl, cea);  // ***** COMPILE ERROR HERE ******
            if(cea.Cancel != true)
                ctl.Validated(ctl, new EventArgs());
        }
        return true;
    }

    foreach(Control ctl2 in ctl.Controls)
        if(ValidateFocusedControlRecursive(ctl2))
            return true;

    return false;
}

Control active = ActiveControl; // called from within your Form
Control next = active.GetNextControl(active, false); // search backward*
next.Focus();
active.Focus();

public void ValidateFocusedControl()
{
    foreach(Control ctl in Controls)
        if(ValidateFocusedControlRecursive(ctl))
            break;
}

bool ValidateFocusedControlRecursive(Control ctl)
{
    if(ctl.Focused)
    {
        if(ctl.CausesValidation)
        {
            // Make current focused control lose focus, and then get
            // it back, so we can force its validation
            TextBox txtBox = new TextBox();
            txtBox.Bounds = new Rectangle(-100, -100, 1, 1);
            txtBox.Parent = ctl.Parent;
            txtBox.Focus();
            ctl.Focus();
            txtBox.Parent = null;
            txtBox.Dispose();
        }
        return true;
    }

    foreach(Control ctl2 in ctl.Controls)
        if(ValidateFocusedControlRecursive(ctl2))
            return true;

    return false;
}

String s = "Lorem ipsum dolor sit amet, kec=123abc";<br />
int index = s.IndexOf("kec=");