Calculate Age based on Date of Birth using C# in ASP.Net

Hi sri.s,

I have created sample that full fill your requirement.

HTML

<table>
    <tr>
        <td>
            <asp:DropDownList ID="ddlYears" runat="server" Width="100">
            </asp:DropDownList>
        </td>
        <td>
            <asp:DropDownList ID="ddlMonths" runat="server" Width="100">
                <asp:ListItem Text="January" Value="1" />
                <asp:ListItem Text="February" Value="2" />
                <asp:ListItem Text="March" Value="3" />
                <asp:ListItem Text="April" Value="4" />
                <asp:ListItem Text="May" Value="5" />
                <asp:ListItem Text="June" Value="6" />
                <asp:ListItem Text="July" Value="7" />
                <asp:ListItem Text="August" Value="8" />
                <asp:ListItem Text="September" Value="9" />
                <asp:ListItem Text="October" Value="10" />
                <asp:ListItem Text="November" Value="11" />
                <asp:ListItem Text="December" Value="12" />
            </asp:DropDownList>
        </td>
        <td>
            <asp:DropDownList ID="ddlDates" runat="server" Width="100">
            </asp:DropDownList>
        </td>
    </tr>
    <tr>
        <td colspan="3" align="center">
            <asp:Button Text="Calculate" runat="server" OnClick="CalculateAge" />
        </td>
    </tr>
    <tr>
        <td>
            You are :
        </td>
        <td colspan="3" align="center">
            <asp:TextBox runat="server" ID="txtAge" Width="220" />
        </td>
    </tr>
</table>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dtYear = new DataTable();
        dtYear.Columns.Add("Year", typeof(int));
        for (int i = 1980; i <= DateTime.Now.Year; i++)
        {
            dtYear.Rows.Add(i);
        }

        ddlYears.DataTextField = "Year";
        ddlYears.DataValueField = "Year";
        ddlYears.DataSource = dtYear;
        ddlYears.DataBind();
        DataTable dtDate = new DataTable();
        dtDate.Columns.Add("Date", typeof(int));
        for (int i = 1; i <= 31; i++)
        {
            dtDate.Rows.Add(i);
        }

        ddlDates.DataTextField = "Date";
        ddlDates.DataValueField = "Date";
        ddlDates.DataSource = dtDate;
        ddlDates.DataBind();
    }
}

protected void CalculateAge(object sender, EventArgs e)
{
    DateTime today = DateTime.Now;
    string year = ddlYears.SelectedValue;
    string month = ddlMonths.SelectedValue;
    string date = ddlDates.SelectedValue;
    DateTime dob = Convert.ToDateTime(month + "/" + date + "/" + year);
    TimeSpan ts = today - dob;
    DateTime age = DateTime.MinValue + ts;
    int years = age.Year - 1;
    int months = age.Month - 1;
    int days = age.Day - 1;
    txtAge.Text = String.Format("{0} year/s {1} month/s {2} day/s old", years, months, days);
}

Screenshot