Insert data in database based value in TextBox in ASP.Net

HTML:

<form id="form1" runat="server">
    <div>
        <asp:TextBox ID="txtAge" runat="server" />
        <asp:Button runat="server" OnClick="Save" Text="Save" />
    </div>
    </form>

 C#:

protected void Save(object sender, EventArgs e)
    {
        string ageDescription = string.Empty;
        int age = Convert.ToInt32(this.txtAge.Text.Trim());
        if (age < 20 && age > 10)
        {
            ageDescription = "between 10-20";
        }
        else if (age < 30 && age > 20)
        {
            ageDescription = "between 20-30";
        }

        //store this ageDescription in table
    }