C#:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
this.label1.Text = "";
this.numericUpDown1.Maximum = 10;
this.numericUpDown1.TextChanged += numericUpDown1_TextChanged;
}
void numericUpDown1_TextChanged(object sender, EventArgs e)
{
if (!Valid(this.numericUpDown1.Text))
this.label1.Text = "Попытка ввесни не верное значение";
else
this.label1.Text = "";
}
bool Valid(string text)
{
int i = 0;
if (!int.TryParse(text, out i))
return false;
if (i < 0 || i > 10)
return false;
else return true;
}
}