Call multiple modal popups from webform in asp.net and c#

I'm trying to call multiple modal popups from a same webform, but I don't want to write them all in the same aspx file, so that's why I thought about using a masterpage.

This is part of the code so far:

<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Trabajadores.master.cs" Inherits="Trabajadores" %>


    <!-- Modal -->
    <div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
        <div class="modal-dialog" role="document">
            <div class="modal-content">
                <asp:ContentPlaceHolder ID="Modal" runat="server">
                </asp:ContentPlaceHolder>
            </div>
        </div>
    </div>
    <!-- Modal -->


                <ul class="nav nav-pills nav-stacked small">
                    <li><a href="~/Empresas/Trabajadores/Ventanas/Empresas.aspx" data-toggle="modal" data-target="#myModal">Empresas</a></li>
                    <li><a href="~/Empresas/Trabajadores/Ventanas/Obras.aspx" data-toggle="modal" data-target="#myModal">Obras</a></li>
                    <li><a href="~/Empresas/Trabajadores/Ventanas/Haberes.aspx" data-toggle="modal" data-target="#myModal">Haberes</a></li>
                    <li><a href="~/Empresas/Trabajadores/Ventanas/Descuentos.aspx" data-toggle="modal" data-target="#myModal">Descuentos</a></li>
                </ul>

And this is one of the modal popups:

<%@ Page Title="Identificación Trabajador" Language="C#" MasterPageFile="~/Trabajadores.Master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Empresas_Trabajadores_Ventanas_Default" %>

<asp:Content ID="BodyContent" ContentPlaceHolderID="Modal" runat="server">

                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                    <h4 class="modal-title" id="myModalLabel">Login</h4>
                </div>
                <div class="modal-body">
                    <form>
                    <div class="form-group">
                        <label>Email address</label>
                        <input type="email" class="form-control" placeholder="Enter Email">
                    </div>
                    <div class="form-group">
                        <label>Password</label>
                        <input type="password" class="form-control" placeholder="Enter Password">
                    </div>
                    </form>
                </div>
                <div class="modal-footer">
                    <button type="submit" class="btn btn-default">Submit</button>
                </div>

</asp:Content>

But it's not working. However, I think if I use a masterpage it will redirect the page in order to open a modal popup, so I'm wondering if there is a way to open multiple modal popups without redirecting the page (so maybe I should not use a materpage, but a c# function instead).