File Upload with Update Panel

ASPX Page

<asp:UpdatePanel ID="UpdatePanel1" runat="server">

            <Triggers>

                <asp:PostBackTrigger ControlID="Button2" />               

            </Triggers>

            <ContentTemplate>

                <asp:Label ID="Label1" runat="server"></asp:Label>

                <asp:FileUpload ID="fupLogo" runat="server" Visible="False"></asp:FileUpload>

                <asp:Button ID="Button2" runat="server" Text="Upload" OnClick="Button2_Click" Visible="False" />

                <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="show Uploader " />

            </ContentTemplate>

        </asp:UpdatePanel>

Code Behind

protected void Button2_Click(object sender, EventArgs e)

    {

        if (fupLogo.HasFile)

        {

            string fileFormat = fupLogo.PostedFile.ContentType;

            Label1.Text = fupLogo.PostedFile.ContentType;

            if (string.Compare(fileFormat, "image/jpeg", true) == 0 ||

            string.Compare(fileFormat, "image/png", true) == 0 ||

            string.Compare(fileFormat, "image/gif", true) == 0)

            {

                Label1.Text += "file format supported<br/>";

            }

            else

            {

                Label1.Text += "file format not supported<br/>";

            }

        }

        else

        {

            Label1.Text += "file not exist<br/>";

        }

    }