Hi nauna,
Refer the below code.
HTML
<div>
<label class="glyphicon glyphicon-open-file">
<asp:FileUpload ID="FileUpload1" runat="server" Style="display: none;"></asp:FileUpload>
</label>
<br />
<asp:Button class="btn btn-success" Text="Save" runat="server" OnClick="Save" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
</div>
Code
protected void Save(object sender, EventArgs e)
{
if (FileUpload1.HasFile)
{
string file = FileUpload1.PostedFile.FileName;
}
}
Screenshot