while the method we use in Substitution control should return strings, so how is it possible to use a donut caching in web forms on a server control which should be rendered server side?
for example Loginview control?
views:
26answers:
2
A:
I'm fairly certain you can't do this - the Substitution control will only allow you to insert a string into an outputcached page.
This makes sense if you think about the whole output of a server control, which could be a <table>
that'll disrupt all your carefully crafted markup and/or something that requires a load of <script>
injected into the page - whereas injecting a single string is something that's relatively straightforward.
PhilPursglove
2010-06-29 07:19:25
+1
A:
UPDATE This is now a fully working example. There a few things happening here:
- Use the call back of a substitution control to render the output of the usercontrol you need.
- Use a custom page class that overrides the VerifyRenderingInServerForm and EnableEventValidation to load the control in order to prevent errors from being thrown when the usercontrol contains server controls that require a form tag or event validation.
Here's the markup:
<asp:Substitution runat="server" methodname="GetCustomersByCountry" />
Here's the callback
public string GetCustomersByCountry(string country)
{
CustomerCollection customers = DataContext.GetCustomersByCountry(country);
if (customers.Count > 0)
//RenderView returns the rendered HTML in the context of the callback
return ViewManager.RenderView("customers.ascx", customers);
else
return ViewManager.RenderView("nocustomersfound.ascx");
}
Here's the helper class to render the user control
public class ViewManager
{
private class PageForRenderingUserControl : Page
{
public override void VerifyRenderingInServerForm(Control control)
{ /* Do nothing */ }
public override bool EnableEventValidation
{
get { return false; }
set { /* Do nothing */}
}
}
public static string RenderView(string path, object data)
{
PageForRenderingUserControl pageHolder = new PageForUserControlRendering();
UserControl viewControl = (UserControl) pageHolder.LoadControl(path);
if (data != null)
{
Type viewControlType = viewControl.GetType();
FieldInfo field = viewControlType.GetField("Data");
if (field != null)
{
field.SetValue(viewControl, data);
}
else
{
throw new Exception("ViewFile: " + path + "has no data property");
}
}
pageHolder.Controls.Add(viewControl);
StringWriter result = new StringWriter();
HttpContext.Current.Server.Execute(pageHolder, result, false);
return result.ToString();
}
}
See these related questions:
Micah
2010-07-23 14:16:13
awesome! thanks
mohamadreza
2010-07-25 08:05:43