//textbox html code
<asp:TextBox ID="TextBox1" runat="server" Style="margin-top: 0px" Width="32px" OnTextChanged="TextBox1_TextChanged" Font-Size="Small" Height="16px">1</asp:TextBox>
//C# embedded code
protected void Page_Load(object sender, EventArgs e)
    {
        TextBox1.TextChanged += TextBox1_TextChanged;
    }
    protected void TextBox1_TextChanged(object sender, EventArgs e)
    {
        DateTime time = new DateTime();
        try
        {
            int textBoxValue = Convert.ToInt32(TextBox1.Text);
            Label2.Text = "valid" + time.ToString("hh:mm:ss");
        }
        catch
        {
            Label2.Text = "test";
            TextBox1.Text = "1";
        }
    }
    protected void TextBox2_TextChanged(object sender, EventArgs e)
    {

    }