Pass Value of Label to another Page on Button click in ASP.Net

Refer Below code for your referance

In Firstpage.aspx

 <form id="form1" runat="server">
    <div>
        <asp:Label ID="lblValue" runat="server" Text="HI"></asp:Label>
        <asp:Button ID="btnredirect" OnClick="btnRedirect_Click" runat="server" />
    </div>
    </form>

 protected void btnRedirect_Click(object sender, EventArgs e)
    {
        string labelvalue;
        labelvalue = this.lblValue.Text.ToString();
        Response.Redirect("~/SecondPage.aspx?labelvalue=" + labelvalue + "");
    }

On SecondPage.aspx

 if (!IsPostBack)
        {
            string FirstPageLabelvalue;
            FirstPageLabelvalue = Request.QueryString["labelvalue"];
}