Hi edaadura,

Check this example. Now please take its reference and correct your code.

HTML

Default

Year:
<asp:DropDownList ID="ddlYear" runat="server">
    <asp:ListItem Selected="True" Value="0">--Select--</asp:ListItem>
    <asp:ListItem Value="2017">2017</asp:ListItem>
    <asp:ListItem Value="2018">2018</asp:ListItem>
</asp:DropDownList>
<br />
Sesi:
<asp:DropDownList ID="ddlSesi" runat="server">
    <asp:ListItem Selected="True" Value="0">--Select--</asp:ListItem>
    <asp:ListItem Value="Sesi 1">Sesi 1</asp:ListItem>
    <asp:ListItem Value="Sesi 2">Sesi 2</asp:ListItem>
</asp:DropDownList>
<br />
<asp:Button ID="btnRedirect" runat="server" Text="Submit" OnClick="btnRedirect_Click" />

Landing Pages

<div>
    Year:<asp:Label ID="lblMessage1" runat="server" Text=""></asp:Label>
    <br />
    Sesi:<asp:Label ID="lblMessage2" runat="server" Text=""></asp:Label>
</div>

Code

C#

Default

protected void btnRedirect_Click(object sender, EventArgs e)
{
    string year = ddlYear.SelectedItem.Text.Trim();
    string sesi = ddlSesi.SelectedItem.Text.Trim();

    Session["year"] = year;
    Session["Sesi"] = sesi;

    if (year == "2017" && sesi == "Sesi 1")
    {
        Response.Redirect("PageA.aspx");
    }
    else if (year == "2017" && sesi == "Sesi 2")
    {
        Response.Redirect("PageB.aspx");
    }
    else if (year == "2018" && sesi == "Sesi 1")
    {
        Response.Redirect("PageC.aspx");
    }
    else if (year == "2018" && sesi == "Sesi 2")
    {
        Response.Redirect("PageD.aspx");
    }
}

Landing Pages

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["year"] != "")
    {
        lblMessage1.Text = Session["year"].ToString();
    }
    if (Session["Sesi"] != "")
    {
        lblMessage2.Text = Session["Sesi"].ToString();
    }
}

VB.Net

Default

Protected Sub btnRedirect_Click(ByVal sender As Object, ByVal e As EventArgs)
    Dim year As String = ddlYear.SelectedItem.Text.Trim()
    Dim sesi As String = ddlSesi.SelectedItem.Text.Trim()
    Session("year") = year
    Session("Sesi") = sesi
    If year = "2017" AndAlso sesi = "Sesi 1" Then
        Response.Redirect("PageA.aspx")
    ElseIf year = "2017" AndAlso sesi = "Sesi 2" Then
        Response.Redirect("PageB.aspx")
    ElseIf year = "2018" AndAlso sesi = "Sesi 1" Then
        Response.Redirect("PageC.aspx")
    ElseIf year = "2018" AndAlso sesi = "Sesi 2" Then
        Response.Redirect("PageD.aspx")
    End If
End Sub

Landing Pages

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Session("year") <> "" Then
        lblMessage1.Text = Session("year").ToString()
    End If

    If Session("Sesi") <> "" Then
        lblMessage2.Text = Session("Sesi").ToString()
    End If
End Sub