Form submit button not working in bootstrap modal window

Submit button is not in the form. Place form="modal-details" to the button, which is form id. You should not have data-dismiss="modal" on submit button, which is a bootstrap handler for closing the modal box. It is working for me.

<div class="modal fade" id="filterModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title" id="exampleModalLabel">Client Filter</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body">
                <form asp-action="Details" asp-controller="Client" method="get" id="modal-details">
                    <div class="form-group">
                        <label for="recipient-name" class="col-form-label">Branch:</label>
                        <select asp-for="NetworkUnitId" class="custom-select form-control">
                            <option value="0">All</option>
                            @foreach (var client in classifierService.GetClients())
                            {
                                <option value="@client.Id">@client.Name</option>
                            }
                        </select>
                    </div>
                </form>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                <button type="submit" class="btn btn-primary" form="modal-details">Search</button>
            </div>
        </div>
    </div>
</div>

Try this using javascript. It worked for me:

 <form name='searchdata' id="search_form" action="search.php" method="get">
                <div class="input-with-icon success-control">  
                    <input type="text" class="form-control" id="form1Amount"     name="searchvalue" placeholder="Search in users or #hashtags"><br/>
                </div>  
                <button onclick="form_submit()" name='user_search' value='user' class="btn btn-danger"><i class="fa fa-user"></i> User</button>
                <button onclick="form_submit()" name='tag_search' value='tag' class="btn btn-default"><i class="fa fa-tag"></i> Tags</button>           
        </form> 

  <script type="text/javascript">
  function form_submit() {
    document.getElementById("search_form").submit();
   }    
  </script>