Hide Modal popup on Button click using jQuery in ASP.Net

Hi nedash,

I have created a sample with your code and its working fine at my side first go through the code thoroughly and implement first in new project and then in your code.

HTML

<div>
    <asp:ScriptManager runat="server" />
    <asp:Image ID="Img6" Visible="false" CssClass="load" ImageUrl="~/Image/admin/createGallery.jpg"
        runat="server" />
    <asp:UpdatePanel runat="server">
        <ContentTemplate>
            <div id="DI1R2">
                <asp:ImageButton ID="Imgdelete6" runat="server" CausesValidation="false" CssClass="DPC9_Img2m"
                    ImageUrl="~/Image/admin/imgdelete.jpg" Visible="false"></asp:ImageButton>
                <asp:Label ID="Lblimg6" runat="server" Visible="false"></asp:Label>
                <asp:Panel ID="Panel5" runat="server">
                    <asp:ModalPopupExtender DropShadow="true" ID="ModalPopupExtender1" PopupControlID="PnPopup6"
                        runat="server" TargetControlID="BtnPopup6" BackgroundCssClass="Modal" CancelControlID="Imgclose">
                    </asp:ModalPopupExtender>
                    <asp:Button ID="BtnPopup6" OnClick="BtnPopup6_Click" runat="server" Text="انتخاب ویدیو"
                        CssClass="DPC9_Img2" BorderStyle="Solid" BorderWidth="0px" BorderColor="White"
                        CausesValidation="false" />
                    <asp:Panel ID="PnPopup6" runat="server" BackColor="White" CssClass="panel" Style="display: none">
                        <div class="CloseImge">
                            <asp:ImageButton ID="Imgclose" runat="server" CssClass="closeI" ImageUrl="~/Image/admin/imgdelete.jpg"
                                CausesValidation="false" />
                        </div>
                        <div class="CloseImge1">
                            <asp:TextBox ID="Txtdes" runat="server" CssClass="txtdesA"></asp:TextBox>
                            <asp:ImageButton ID="ImageButton15" OnClick="BtnUploadL6_Click" runat="server" CausesValidation="false"
                                ImageUrl="~/Image/admin/createGallery.jpg" CssClass="load" />
                        </div>
                    </asp:Panel>
                </asp:Panel>
        </ContentTemplate>
    </asp:UpdatePanel>
</div>
<div>
    <style type="text/css">
        .DPC9_Img2
        {
            margin: 5px 22px 0 0;
            background-color: White;
            cursor: pointer;
            float: right;
            height: 25px;
            font-size: 14.5px;
        }
            
        .CloseImge
        {
            float: right;
            width: 300px;
        }
        .closeI
        {
            float: right;
            width: 22px;
            height: 22px;
            margin: 5px 10px 0 0;
        }
        #CloseImge1
        {
            float: right;
            width: 500px;
        }
            
        .Modal
        {
            background-color: #2a2a23;
            opacity: 0.5;
        }
        .panel
        {
            background: url(../image/admin/popup1.png) no-repeat;
            float: right;
            width: 531px;
            height: 118px;
        }
        .load
        {
            width: 100px;
            height: 70px;
        }
        .txtdesA
        {
            border: 1px solid #575757;
            float: right;
            margin: 18px 65px 0 0;
            background-color: White;
            direction: rtl;
            width: 240px;
            font-size: 14px;
        }
    </style>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        $(function () {
            $('[id*=ImageButton15]').click(function () { //ImageButton15 is Id of ImageButton.
                $('[id*=ModalPopupExtender1]').hide();
            });
        });
    </script>
</div>

C#

protected void BtnPopup6_Click(object sender, EventArgs e)
{
    ModalPopupExtender1.Show();
}

protected void BtnUploadL6_Click(object sender, EventArgs e)
{
    Lblimg6.Text = Txtdes.Text;
    Lblimg6.Visible = true;
    Img6.Visible = true;
    Imgdelete6.Visible = !(BtnPopup6.Visible = false);
    Img6.Visible = true;
}

VB.Net

Protected Sub BtnPopup6_Click(sender As Object, e As EventArgs)
	ModalPopupExtender1.Show()
End Sub

Protected Sub BtnUploadL6_Click(sender As Object, e As EventArgs)
	Lblimg6.Text = Txtdes.Text
	Lblimg6.Visible = True
	Img6.Visible = True
	Imgdelete6.Visible = Not (InlineAssignHelper(BtnPopup6.Visible, False))
	Img6.Visible = True
End Sub

Screenshot