Dropdownlist always return the first item

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ASP.NET

DropDownList

C#7.0

When I want to get the data which the user selected in the third ddl, it always return me the first item.

When user select Game from ddl1 and B from ddl2, the ddl3 will populate the option, but ddl3.selecteditem.text will always return me Dota although the user select LoL as their option.

Is that anyway I can solve this issue? Any suggestion will be a great help. Thanks !

What I have tried:

Here is the ddl1 :

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack ="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
<asp:ListItem Text="-- Select One --"></asp:ListItem>
<asp:ListItem Text="Game"></asp:ListItem>
<asp:ListItem Text="Book"></asp:ListItem>

Here is the function for ddl3:

protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
   {
       DropDownList3.Visible = true;
       if (DropDownList2.SelectedValue == "A")
       {
           DropDownList3.Items.Clear();
           DropDownList3.Items.Insert(0, new ListItem("-Select-", "N"));
           DropDownList3.Items.Insert(1, new ListItem("CSGO", ""));
           DropDownList3.Items.Insert(2, new ListItem("CSO", ""));
           DropDownList3.Items[0].Attributes["disabled"] = "disabled";
       }
       else if (DropDownList2.SelectedValue == "B")
       {
           DropDownList3.Items.Clear();
           DropDownList3.Items.Insert(0, new ListItem("-Select-", "N"));
           DropDownList3.Items.Insert(1, new ListItem("Dota", ""));
           DropDownList3.Items.Insert(2, new ListItem("LoL", ""));