❔ Element's class in Master not changing

<li id="list_home" runat="server" class="active">
    <asp:Button ID="home_button" runat="server" Text="Home" OnClick="home_button_Click"/>
</li>
<li id="list_catalog" runat="server">
    <asp:Button ID="catalog_button" runat="server" Text="Catalog" OnClick="catalog_button_Click" />
</li>
<li id="list_purchase" runat="server">
    <asp:Button ID="purchase" runat="server" Text="Purchase" OnClick="purchase_Click" />
</li>
<li id="list_profile" style="float:right"><a id="profile">Profile</a></li>

private HtmlGenericControl prev = null;
protected void Page_Load(object sender, EventArgs e)
{
    
}

protected void home_button_Click(object sender, EventArgs e)
{
    list_home.Attributes["class"] = "active";

    if(this.prev != null)
    {
        prev.Attributes["class"] = "";
    }
    prev = list_home;
    Response.Redirect("home.aspx");
}

protected void catalog_button_Click(object sender, EventArgs e)
{
    list_catalog.Attributes["class"] = "active";

    if (this.prev != null)
    {
        prev.Attributes["class"] = "";
    }
    prev = list_catalog;
    Response.Redirect("catalog.aspx");
}

protected void purchase_Click(object sender, EventArgs e)
{
    list_purchase.Attributes["class"] = "active";

    if (this.prev != null)
    {
        prev.Attributes["class"] = "";
    }
    prev = list_purchase;
    Response.Redirect("purchase.aspx");
}
}