<% @Control Language="C#" %>
    <script language="C#" runat="server">
        void btnDecrease_Click(Object Src, EventArgs E)
        {
            int CurrentValue = GetCurrentValue();
            CurrentValue--;
            txtValue.Text = CurrentValue.ToString();
        }

        void btnIncrease_Click(Object Src, EventArgs E)
        {
            int CurrentValue = GetCurrentValue();
            CurrentValue++;
            txtValue.Text = CurrentValue.ToString();
        }

        int GetCurrentValue()
        {
            try
            {
                return Convert.ToInt32(txtValue.Text);
            }
            catch( Exception )
            {
                return 0; // Return 0 if txtValue.Text is not numeric
            }
        }
</script>

<form runat=server>
    <asp:Button id="btnDecrease" text="Decrease" onclick="btnDecrease_Click" runat="server"/>
    <asp:TextBox id="txtValue" runat="server" value="0" />
    <asp:Button id="btnIncrease" text="Increase" onclick="btnIncrease_Click" runat="server"/>
</form>