Private Sub C1ComboBox1_GotFocus(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles C1ComboBox1.GotFocus
　　Dim tb = TryCast(e.OriginalSource, C1.Silverlight.C1TextBoxBase)
　　If tb IsNot Nothing Then
　　　　Dim etb As C1.Silverlight.C1TextBoxBase = tb
　　　　RemoveHandler tb.TextChanged, New TextChangedEventHandler(AddressOf tb_TextChanged)
　　　　AddHandler tb.TextChanged, New TextChangedEventHandler(AddressOf tb_TextChanged)
　　End If
End Sub

Private Sub tb_TextChanged(sender As Object, e As TextChangedEventArgs)
　　Dim tb As C1.Silverlight.C1TextBoxBase = TryCast(sender, C1.Silverlight.C1TextBoxBase)
　　If Not isNumeric(tb.C1Text, System.Globalization.NumberStyles.[Integer]) Then
　　　　MessageBox.Show(tb.Text + "：無効な値です。数値を入力してください。")
　　　　tb.C1Text = Nothing
　　End If
End Sub

Public Function isNumeric(val As String, NumberStyle As System.Globalization.NumberStyles) As Boolean
　　Dim result As [Double]
　　Return [Double].TryParse(val, NumberStyle, System.Globalization.CultureInfo.CurrentCulture, result)
End Function

private void c1ComboBox1_GotFocus(object sender, RoutedEventArgs e)
{
　　var tb = e.OriginalSource as C1.Silverlight.C1TextBoxBase;
　　if (tb != null)
　　{
　　　　C1.Silverlight.C1TextBoxBase etb = tb;
　　　　tb.TextChanged -= new TextChangedEventHandler(tb_TextChanged);
　　　　tb.TextChanged += new TextChangedEventHandler(tb_TextChanged);
　　}
}

private void tb_TextChanged(object sender, TextChangedEventArgs e)
{
　　C1.Silverlight.C1TextBoxBase tb = sender as C1.Silverlight.C1TextBoxBase;
　　if (!isNumeric(tb.C1Text, System.Globalization.NumberStyles.Integer))
　　{
　　　　MessageBox.Show(tb.C1Text +" ：無効な値です。数値を入力してください。");
　　　　tb.C1Text = null;
　　}
}

public bool isNumeric(string val, System.Globalization.NumberStyles NumberStyle)
{
　　Double result;
　　return Double.TryParse(val, NumberStyle, System.Globalization.CultureInfo.CurrentCulture, out result);
}