Hi ashish007,

Check below sample.

HTML

<asp:DataList ID="DataList1" runat="server" RepeatColumns="2" 
    HorizontalAlign="Center" RepeatDirection="Horizontal" CellSpacing="3">
    <ItemTemplate>
        <table>
            <tr>
                <td>
                    <asp:Label runat="server" Text='<%#Eval("FirstName") %>'></asp:Label>
                    <asp:Label runat="server" Text='<%#Eval("LastName") %>'></asp:Label>
                    <br /><br />
                    <asp:Label ID="lblbday" runat="server" Text="Birthday" Font-Bold="true" ForeColor="Green"></asp:Label>
                </td>
            </tr>
        </table>
    </ItemTemplate>
</asp:DataList>

Namespaces

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindData();
    }
}

private void BindData()
{
    DataSet odt = new DataSet();
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[] {
            new DataColumn("Id"), new DataColumn("FirstName"),
            new DataColumn("LastName"), new DataColumn("D_O_B") });
    dt.Rows.Add(1, "Ram", "Sharma", "17/11/1984");
    dt.Rows.Add(2, "Ashish", "Khan", "23/11/1984");
    odt.Tables.Add(dt);
    if (odt.Tables[0].Rows.Count > 0)
    {
        DataList1.DataSource = odt;
        DataList1.DataBind();
        for (int i = 0; i < odt.Tables[0].Rows.Count; i++)
        {
            string db = odt.Tables[0].Rows[i]["D_O_B"].ToString();
            string[] strarr = db.Split('/');
            int day = Int32.Parse(strarr[0]);
            int month = Int32.Parse(strarr[1]);
            int year = Int32.Parse(strarr[2]);
            string someDate = Convert.ToString(year + "/" + month + "/" + day);
            DateTime startDate = DateTime.Parse(someDate);
            DateTime now = DateTime.Now;
            if (startDate.Month == now.Month)
            {
                int birthDate = startDate.Day;
                int todayDate = now.Day;
                if (birthDate > todayDate)
                {
                    DataListItem item = DataList1.Items[i];
                    Label lblday = item.FindControl("lblbday") as Label;
                    lblday.Text = "Birth Day come in " + (birthDate - todayDate).ToString() + " days.";
                }
            }
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.BindData()
    End If
End Sub

Private Sub BindData()
    Dim odt As DataSet = New DataSet()
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn() {
                        New DataColumn("Id"), New DataColumn("FirstName"),
                        New DataColumn("LastName"), New DataColumn("D_O_B")})
    dt.Rows.Add(1, "Ram", "Sharma", "17/11/1984")
    dt.Rows.Add(2, "Ashish", "Khan", "23/11/1984")
    odt.Tables.Add(dt)
    If odt.Tables(0).Rows.Count > 0 Then
        DataList1.DataSource = odt
        DataList1.DataBind()
        For i As Integer = 0 To odt.Tables(0).Rows.Count - 1
            Dim db As String = odt.Tables(0).Rows(i)("D_O_B").ToString()
            Dim strarr As String() = db.Split("/"c)
            Dim day As Integer = Int32.Parse(strarr(0))
            Dim month As Integer = Int32.Parse(strarr(1))
            Dim year As Integer = Int32.Parse(strarr(2))
            Dim someDate As String = Convert.ToString(year & "/" & month & "/" & day)
            Dim startDate As DateTime = DateTime.Parse(someDate)
            Dim now As DateTime = DateTime.Now
            If startDate.Month = now.Month Then
                Dim birthDate As Integer = startDate.Day
                Dim todayDate As Integer = now.Day
                If birthDate > todayDate Then
                    Dim item As DataListItem = DataList1.Items(i)
                    Dim lblday As Label = TryCast(item.FindControl("lblbday"), Label)
                    lblday.Text = "Birth Day come in " & (birthDate - todayDate).ToString() & " days."
                End If
            End If
        Next
    End If
End Sub

Screenshot