How to persist or hold multiple values across PostBack in ASP.Net

Here i am using one example to show you how i am preserving the selected values of DropDownList and ListBox using Disctionary and ViewState. I am having three season values in DropDownList and ListBox contains Season fruites. On Button Click i am storing these values in ViewSate

HTML:

<form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddlSeasons" runat="server">
            <asp:ListItem Text="Summer" Value="0" />
            <asp:ListItem Text="Winter" Value="1" />
            <asp:ListItem Text="Rainy" Value="2" />
        </asp:DropDownList>
        <asp:ListBox ID="lbFruites" runat="server">
            <asp:ListItem Text="Mango" Value="0" />
            <asp:ListItem Text="Apple" Value="1" />
            <asp:ListItem Text="Banana" Value="2" />
            <asp:ListItem Text="Orange" Value="2" />
        </asp:ListBox>
        <asp:Button runat="server" OnClick="Save" Text="Save" />
    </div>
    </form>

C#:

protected void Save(object sender, EventArgs e)
        {
            if (ViewState["SelectedValues"] == null)
            {
                Dictionary<string, string> dictionary = new Dictionary<string, string>();
                dictionary.Add(this.ddlSeasons.SelectedItem.Text, this.lbFruites.SelectedItem.Text);
                ViewState["SelectedValues"] = dictionary;
            }

            else
            {
                Dictionary<string, string> dictionary = (Dictionary<string, string>)ViewState["SelectedValues"];
                dictionary.Add(this.ddlSeasons.SelectedItem.Text, this.lbFruites.SelectedItem.Text);
                ViewState["SelectedValues"] = dictionary;
            }

        }

Image:

first i have selected Summer and Mango the i select Winter and apple so i am storing these values in Dictionary.

Thank You.