I ran into this a while back when dealing with the ParseControl and
LoadControl methods. The ParseConrol always returns a Contol, no matter
what I was parsing. After you perform a Controls.Add() with a control
returned from ParseControl, the actual object instance in the controls
collection is a new/different reference. This is the oposite behavior of
the LoadControl, which returns the actual underlying class type. After you
add a control using LoadControl, the instance in the controls collection is
the same as that returned from LoadControl. My work around for this was to
add one more step to the process:
System.Web.UI.Control myForm = Page.FindControl("WebForm1");
System.Web.UI.Control ctl = Page.ParseControl("<asp:Button runat=\"server\"
id=\"test\" />");
myForm.Controls.Add(ctl);
// get that bad boy back
Button btn = (Button)myForm.FindControl("test");
It seems the framework detects the fact that the control being added has a
base type of Control and performs an additional few steps in determining
the Control's "real" type, creating a new instance of that type and adding
that instead.
On Tue, 17 Sep 2002 15:14:33 -0400, Kirk Allen Evans
<[EMAIL PROTECTED]> wrote:
>Frustrating, I can't think offhand why the cast is invalid either. A
>quick workaround is to specify the property of the control when it is
>being parsed instead of trying to cast to set the property as an object:
>
>System.Web.UI.Control myForm = Page.FindControl("WebForm1");
>
>System.Web.UI.Control ctl = Page.ParseControl("<asp:Button
>runat=\"server\" id=\"test\" text=\"Hello, World!\"/>");
>
>myForm.Controls.Add(ctl);
>
>
>Kirk Allen Evans
>http://www.xmlandasp.net
>Author, "XML And ASP.NET", New Riders Publishing
>http://www.amazon.com/exec/obidos/ASIN/073571200X
>
>> -----Original Message-----
>> From: Moderated discussion of advanced .NET topics. [mailto:ADVANCED-
>> [EMAIL PROTECTED]] On Behalf Of Steven Livingstone
>> Sent: Tuesday, September 17, 2002 1:59 PM
>> To: [EMAIL PROTECTED]
>> Subject: Re: [ADVANCED-DOTNET] Controls, .Net and Xslt insanity
>>
>> Ok, what is wrong with this example from the SDK? Invalid Cast
>exception
>> at the line marked ***. Do you have a working example or a pointer to
>> one :)
>>
>> <%@ Page language="c#" %>
>> <html>
>> <head>
>> <script language="C#" runat="server">
>> void Page_Load(object sender, System.EventArgs
>> e)
>> {
>> Button myButton =
>> (Button)ParseControl("<asp:button runat = \"server\"/>"); //***
>> myButton.Text = "Hello World!";
>> Controls.Add(myButton);
>> }
>>
>> private void button_OnClick(object sender,
>> System.EventArgs e)
>> {
>> }
>> </script>
>> </head>
>> </html>
>>
>> -----Original Message-----
>> From: Moderated discussion of advanced .NET topics.
>> [mailto:[EMAIL PROTECTED]] On Behalf Of Kirk Allen
>> Evans
>> Sent: 17 September 2002 18:51
>> To: [EMAIL PROTECTED]
>> Subject: Re: [ADVANCED-DOTNET] Controls, .Net and Xslt insanity
>>
>>
>> No, it is a string. Retrieve your output from the transformation as a
>> string, and parsecontrol can load that string in. The example in the
>> SDK is actually a good representation of how to do it, since it is
>> simple. The key is to get the XSLT out as a string so that it can be
>> loaded into Page.ParseControl.
>>
>> Remember to either have a form element declared in the .ASPX page and
>> add controls to it, or dynamically add it and use Page.Controls.Add
>> method to add the form and its child controls.
>>
>> Kirk Allen Evans
>> http://www.xmlandasp.net
>> Author, "XML And ASP.NET", New Riders Publishing
>> http://www.amazon.com/exec/obidos/ASIN/073571200X
>>
>> > -----Original Message-----
>> > From: Moderated discussion of advanced .NET topics.
>[mailto:ADVANCED-
>> > [EMAIL PROTECTED]] On Behalf Of Steven Livingstone
>> > Sent: Tuesday, September 17, 2002 1:28 PM
>> > To: [EMAIL PROTECTED]
>> > Subject: Re: [ADVANCED-DOTNET] Controls, .Net and Xslt insanity
>> >
>> > Hi Kirk -
>> > Yep - that is exactly the way I want to do it. Any good examples of
>> > working with the ParseControl? The MSDN ones fail with a cast
>> exception.
>> > The LoadControl() would be cool if it took a MemoryStream - but it
>> > doesn't :(
>> >
>> > I think that if Xslt was better integrated with the IDE we could
>have
>> > pretty powerful server controls. I've stayed away from server
>> > controls, but now I am finding the fun in trying to work with them
>> > with the Xslt knowledge I have.
>> >
>> > Thanks,
>> > Steven
>> >
>> > -----Original Message-----
>> > From: Moderated discussion of advanced .NET topics.
>> > [mailto:[EMAIL PROTECTED]] On Behalf Of Kirk Allen
>> > Evans
>> > Sent: 17 September 2002 18:01
>> > To: [EMAIL PROTECTED]
>> > Subject: Re: [ADVANCED-DOTNET] Controls, .Net and Xslt insanity
>> >
>> >
>> > One way to do this is to use the Page.ParseControl and Controls.Add
>> > methods to load the controls that are dynamically created. The
>> downside
>> > to the approach is that the web forms controls are prefixed with
>> "asp:",
>> > but the page has no namespace declaration associated with the
>> namespace
>> > prefix "asp". So, you have to fake one in your XSLT, then remove it
>> so
>> > that Page.ParseControl doesn't throw an exception. So, you have to
>> > implement some sort of a post-processor on your XSLT result as a
>> string
>> > to remove the xmlns declaration for the dummy namespace bound to the
>> asp
>> > prefix, but leaving the asp prefix on all nodes. Or, you can output
>> > elements as HTML with an additional "runat='server'" attribute and
>> pass
>> > them into the Page.ParseControl method, enabling them to become HTML
>> > server controls. Performance takes a hit, but I couldn't pinpoint
>any
>>
>> > huge glaring performance issues with small test sets.
>> >
>> > Personally, I prefer a mixed approach, using XML to load into
>DataSets
>>
>> > that are bound to UI elements as well as to use XSLT for limited
>> display
>> > areas instead of entire pages.
>> >
>> > Kirk Allen Evans
>> > http://www.xmlandasp.net
>> > Author, "XML And ASP.NET", New Riders Publishing
>> > http://www.amazon.com/exec/obidos/ASIN/073571200X
>> >
>> > > -----Original Message-----
>> > > From: Moderated discussion of advanced .NET topics.
>> [mailto:ADVANCED-
>> > > [EMAIL PROTECTED]] On Behalf Of Steven Livingstone
>> > > Sent: Tuesday, September 17, 2002 12:02 PM
>> > > To: [EMAIL PROTECTED]
>> > > Subject: [ADVANCED-DOTNET] Controls, .Net and Xslt insanity
>> > >
>> > > Ok, even after taking time out again to think about this issue I
>> feel
>> > I
>> > > need some view and opinions.
>> > > Creating web controls in .Net - when and how?
>> > >
>> > > For years now I have almost without exception used Xslt to
>generate
>> > the
>> > > output for forms and content alike. Now, with web controls there
>is
>> > the
>> > > mixed content and code, some of which I don't like all that much.
>To
>>
>> > > generate a menu for example, I would be more tempted to write the
>> code
>> >
>> > > to use Xslt to transform the data. The idea of writing out table
>> > > elements in C# code with javascript inserted as strings is not at
>> all
>> > > appealing.
>> > >
>> > > When it comes to forms, it is more appealing as you can get state
>> > > management and validation - both of which are a pain to manage in
>> > Xslt.
>> > > Still you have the annoying need to write out table elements and
>> form
>> > > elements (e.g. output.Write("<td class='clsMenuBarCell'
>nowrap>");)
>> > >
>> > > I have hit one of those mind block days where I am arguing with
>> myself
>> >
>> > > over the better way to do things, so it's out to the jury to let
>me
>> > know
>> > > what you have been doing.
>> > > I'm pretty sure the best way is some combination - this would
>> ideally
>> > be
>> > > a way of still getting state management and validation, with OO,
>but
>>
>> > > being able to separate the display from the Asp.Net, but this
>> doesn't
>> > > seem possible.
>> > >
>> > > I also dislike the idea of transforming to an aspx page and then
>> > loading
>> > > that.
>> > >
>> > > Has anyone looked at in memory dynamic compilation? In other
>words,
>> > > still having your xslt's that can be loaded. These transform to an
>> > aspx
>> > > output in memory that is dynamically returned so that you can
>still
>> > get
>> > > all the benefits of state management and validation methods? An
>> > example
>> > > may be:
>> > >
>> > > - user vists page
>> > > - aspx page generates form using Xml data and Xslt to create aspx
>> code
>> > > - user submits data
>> > > - aspx code behind validates and maintains viewstate
>> > > - in memory aspx output section is modified by code-behind (e.g.
>> > > label.Text="Invalid Telephone Number")
>> > > - result is sent to the output
>> > >
>> > > Thanks,
>> > > Steven.
>> > >
>> > >
>> > > ==========================================================
>> > > Steven Livingstone BSc (hons), PgDip ITS
>> > [[EMAIL PROTECTED]]
>> > > .Net & Xml Consultant
>> > >
>> > > Change your business at http://www.deltabis.net
>> > > Grow your business at http://www.venturetogether.com
>> > > Change European Football at http://www.theatlanticleague.com
>> > >
>> > > *** Author of "Application Development with MSXML 4.0"
>> > > *** Coming Soon to a developer near you...
>> > > "Beg VB.NET XML:Essential XML Skills for VB.NET Programmers" "Beg
>C#
>>
>> > > XML:Essential XML Skills for C# Programmers"
>> > > ==========================================================
>> > >
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