Close Bootstrap Modal Popup On Button Click in ASP.Net using C# and VB.Net

Hi ramco1917,

You need to close the modal from code behind.

Refer below example.

HTML

<div class="container-fluid" style="margin-top: 20px;">
    <asp:Button ID="btnOpen" runat="server" class="btn bg-primary" Text="Open" OnClientClick="ShowModal();return false;" />
    <div id="MyPopup" class="modal fade" role="dialog">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <h4 class="modal-title">Add Nominee</h4>
                    <button type="button" class="close" data-dismiss="modal">&times;</button>&nbsp;
                <div class="form-horizontal">
                    <div class="modal-body" style="padding-left: 40px; padding-right: 20px;">
                        <div class="row">
                            <div class="col-lg-6">
                            </div>
                            <div class="modal-body">
                                <label>Nominee</label>&nbsp;<span style="color: red">*</span>
                                <asp:ListBox ID="lstNominee" runat="server" data-placeholder="Choose Nominee"
                                    class="form-control multiselect-full-featured" multiple="multiple"
                                    SelectionMode="Multiple" data-fouc=""></asp:ListBox>
                            </div>
                            <div class="modal-footer">
                                <button type="button" class="btn btn-link" data-dismiss="modal">Close</button>
                                <asp:Button ID="btnSave" runat="server" class="btn bg-primary" Text="Save" OnClick="btnSubmit_Click" />
                            </div>
                        </div>
                    </div>
                </div>
                </div>
            </div>
        </div>
    </div>
</div>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<script type="text/javascript">
    function CloseModal() {
        $("#MyPopup").modal("hide");
    }
    function ShowModal() {
        $("#MyPopup").modal("show");
    }
</script>

Code

C#

protected void btnSubmit_Click(object sender, EventArgs e)
{
    ClientScript.RegisterStartupScript(this.GetType(), "alert", "CloseModal();", true);
}

VB.Net

Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As EventArgs)
    ClientScript.RegisterStartupScript(Me.GetType(), "alert", "CloseModal();", True)
End Sub

Screenshot