How to get the value using the linkbutton that was inside the gridview

<pre><div id="id01" class="modal">
        <form class="modal-content animate">
      
            <div class="imgcontainer"></div>
            <span onclick="document.getElementById('id01').style.display='none'" class="close" title="Close Modal">×</span>
            <div class="container"> 
               <p> This message was rejected by the recipient email system. Please check the recipient's email address and  try resending this message, or contact the recipient directly</p>
                <p> A problem occurred while delivering this message to this email address. Try sending this message again. If the problem continues, please contact your helpdesk.</p>
                <p> The domain name in the email address is incorrect. Check the address.</p>
                <p> Sorry, I couldn't find any host named like(Sample@email.com). Please check the email address and try again.</p>
                <p> The server has tried to deliver this message, without success, and has stopped trying. Please try sending this message again.<br /> If the problem continues, contact your helpdesk.</p>
                <button type="button" runat="server" onclick="document.getElementById('id01').style.display='none'" id="btncancel">Cancel</button>
                <br />
                <asp:Label runat="server" ID="lblError"></asp:Label>
            </div>
        </form>
    </div>

<pre><form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" BackColor="White" BorderColor="#CC9966" BorderStyle="None" BorderWidth="1px" CellPadding="4" OnRowCommand="GridView1_RowCommand" OnSelectedIndexChanged="GridView1_SelectedIndexChanged">
            <Columns>
                <asp:TemplateField HeaderText="Subject">
                    <ItemTemplate>
                       <<pre><asp:LinkButton ID="LinkButton1"  runat="server" CommandArgument="EmailDetails" CommandName="DisplayEmail" Text='<%# Eval("Subject") %>'></asp:LinkButton>
                    
                
                <%--<asp:BoundField DataField="Subject" HeaderText="Subject Email" />--%>
                <asp:BoundField DataField="Sender" HeaderText="Receiver" />
                <asp:BoundField DataField="DateCreated" HeaderText="Date and Time Sent" />
                <asp:BoundField DataField="DateReceive" HeaderText="Date and Time Received" />
                <asp:BoundField DataField="EmailHeader" HeaderText="Details" />
            
            <FooterStyle BackColor="#FFFFCC" ForeColor="#330099" />
            <HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="#FFFFCC" />
            <PagerStyle BackColor="#FFFFCC" ForeColor="#330099" HorizontalAlign="Center" />
            <RowStyle BackColor="White" ForeColor="#330099" />
            <SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="#663399" />
            <SortedAscendingCellStyle BackColor="#FEFCEB" />
            <SortedAscendingHeaderStyle BackColor="#AF0101" />
            <SortedDescendingCellStyle BackColor="#F6F0C0" />
            <SortedDescendingHeaderStyle BackColor="#7E0000" />
        
    <asp:Label runat="server" ID="lblSubject">

<button onclick="document.getElementById('id01').style.display='block'" runat="server">List Email Errors</button>

<pre> <script>
    // Get the modal
    var modal = document.getElementById('id01');
    var modal = document.getElementById('id02');
    // When the user clicks anywhere outside of the modal, close it
    window.onclick = function(event) {
    if (event.target == modal) {
    modal.style.display = "none";
    }
    }
    </script>

document.getElementById('id01')

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
       {
           if (e.CommandName == "DisplayEmail")
           {


           }

           }