Bootstrap Modal Popup not opening on LinkButton Click from code behind in ASP.Net

Hi AbdulHaque,

I have checked. Your code is working.

Check with below sample code.

HTML

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
<script type="text/javascript">
    function openModal() {
        $('[id*=myModal]').modal('show');
    }
</script>
<div>
    <div id="myModal" class="modal fade" role="dialog">
        <div class="modal-dialog">
            <!-- Modal content-->
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal">
                        &times;</button>
                    <h4 class="modal-title">
                        Modal Header</h4>
                </div>
                <div class="modal-body">
                    <iframe id="Iframe1" runat="server"></iframe>
                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-default" data-dismiss="modal">
                        Close</button>
                </div>
            </div>
        </div>
    </div>
    <div class="panel panel-default">
        <div class="panel-heading">
            <b>ADM Details</b> <span style="float: right" data-toggle="collapse" data-target="#admDetails"
                class="glyphicon glyphicon-minus"></span>
            <asp:LinkButton ID="LinkButton1" runat="server" OnClick="lbADM_Click">Edit</asp:LinkButton>
            <asp:LinkButton ID="LinkButton2" runat="server" data-toggle="modal" data-target="#myModal"
                OnClick="lbTechnical_Click">EditTech</asp:LinkButton>
        </div>
        <div class="panel-body collapse in" id="admDetails">
            <div class="row">
                <div class="col-lg-4 col-md-4 col-sm-12">
                    <asp:Label ID="lbAdmAppDate" runat="server" Text="ADM Approval" CssClass="lbl1"></asp:Label>
                    <asp:Label ID="lblAdmApprovalDate" runat="server" Text="-" CssClass="lbl2"></asp:Label>
                </div>
                <div class="col-lg-4 col-md-4 col-sm-12">
                    <asp:Label ID="lbAdmAmt" runat="server" Text="ADM Amount" CssClass="lbl1"></asp:Label>
                    <asp:Label ID="lblAdmAmount" runat="server" Text="-" CssClass="lbl2"></asp:Label>
                </div>
                <div class="col-lg-4 col-md-4 col-sm-12">
                    <br style="line-height: 50px" />
                    <asp:HyperLink runat="server" ID="hplAdmDetails" Text="Edit" CssClass="hpl" Visible="false"></asp:HyperLink>
                    <asp:LinkButton ID="lbADM" runat="server" Text="Edit" CssClass="hpl" OnClick="lbADM_Click">Edit</asp:LinkButton>
                </div>
            </div>
        </div>
    </div>
</div>

C#

protected void lbADM_Click(object sender, EventArgs e)
{
    Iframe1.Attributes.Add("src", "AdmDetails.aspx");
    ScriptManager.RegisterStartupScript(this, this.GetType(), "Pop", "openModal();", true);
}

protected void lbTechnical_Click(object sender, EventArgs e)
{
    Iframe1.Attributes.Add("src", "AdmDetails.aspx");
    ScriptManager.RegisterStartupScript(this, this.GetType(), "Pop", "openModal();", true);
}

VB.Net

Protected Sub lbADM_Click(ByVal sender As Object, ByVal e As EventArgs)
    Iframe1.Attributes.Add("src", "AdmDetails.aspx")
    ScriptManager.RegisterStartupScript(Me, Me.GetType(), "Pop", "openModal();", True)
End Sub

Protected Sub lbTechnical_Click(ByVal sender As Object, ByVal e As EventArgs)
    Iframe1.Attributes.Add("src", "AdmDetails.aspx")
    ScriptManager.RegisterStartupScript(Me, Me.GetType(), "Pop", "openModal();", True)
End Sub

Screenshot