How I can see a Image in my ImageButton?

Question

I write a ASP.NET Application for creating a signatur and other stuff. And I use the AjaxToolkit with the CalenderExtender. I want if I click on a ImageButton that open the extender and the TextBox get the Data. It works fine but I don't see the ButtonImage :( >.<

Where I can get a Image for my ImageButton and how it works? Here my ASPX Site Code

 ...
<tr>
                                <td>Abwesenheit von: </td><td>
                                <asp:TextBox ID="txtAbwesenheitVon" runat="server" Enabled="false"></asp:TextBox>
                                <asp:ImageButton ID="imgbtnAbwesenheitVon" runat="server" ToolTip="Abwesenheit von..." PostBackUrl="~/App_Theme/Calender.ico" />
                                <asp:CalendarExtender ID="AbwesenheitVon" runat="server" TargetControlID="txtAbwesenheitVon" 
                                                      Format="dd.MM.yyyy" PopupButtonID="imgbtnAbwesenheitVon"></asp:CalendarExtender>
                                </td>
                                </tr>
    ...

My second Question is. Can I use a Label for the textBox, too?

But I see only this..._->

Answer 1

Replace

PostBackUrl="~/App_Theme/Calender.ico"

with

ImageUrl = "~/App_Theme/Calender.ico"

Image.ImageUrl Property

Answer 2

使用ImageUrl属性代替PostBackUrl