Custom control: How to render an embedded image at design-time?

[Justin]

Hi,

I have a custom web server control, specifically a composite control,
that includes an image button. The image button takes an ImageUrl
property that renders at _runtime_, but at design-time the image does
not render unless the user chooses an image.

I would like to display a default image at design-time (or _at_least_
reduce the size of the "missing image" icon that Visual Studio
displays--it is too big**[see footnote]**).

The ImageUrl property can only point to a path, obviously, which means
I must depend on the user to have an image at a certain path. Also, I
cannot access the Request object (thus neither the
Request.ApplicationPath) at design-time, so I can't even get a valid
path at design-time anyways.

Therefore, I would like to use an embedded resource (an image included
in the Visual Studio project, with 'Build Action' marked as "Embedded
Resource") at runtime.

But from what I can tell, System.Web.UI.Design.ControlDesigner only
allows me to really affect the HTML at design-time via
GetDesignTimeHtml(). But I cannot display an embedded resource with
HTML...

Here are relevant parts of my code:

---------------------------------------------

public class PopupCalendar : System.Web.UI.WebControls.WebControl,
INamingContainer {
private TextBox textBox;
private Image image;

....

protected override void CreateChildControls() {
this.Controls.Clear();
textBox = new TextBox();
this.Controls.Add(textBox);
textBox.ID = "TextBox";

image = new Image();
this.Controls.Add(image);
image.ID = "Image";

}

....

}

---------------------------------------------

public class PopupCalendarDesigner : WebDesign.ControlDesigner {
public override string GetDesignTimeHtml () {
PopupCalendar popcal = (PopupCalendar)this.Component;

return "<input type=\"text\" style=\"width: " +
popcal.Width + "px\"
/><img style=\"width: 16px; height: 16px;\">";
}

}

---------------------------------------------

**[footnote]**
I have tried putting "image.Width = Unit.Pixel(16); image.Height =
Unit.Pixel(16);" in CreateChildControls(), but that means that only
16x16 images can be used, because this affects _both_ design-time and
run-time.

Thank you very much for your help!

- Justin

 

[Mythran]

Hi,

I have a custom web server control, specifically a composite control,
that includes an image button. The image button takes an ImageUrl
property that renders at _runtime_, but at design-time the image does
not render unless the user chooses an image.

I would like to display a default image at design-time (or _at_least_
reduce the size of the "missing image" icon that Visual Studio
displays--it is too big**[see footnote]**).

The ImageUrl property can only point to a path, obviously, which means
I must depend on the user to have an image at a certain path. Also, I
cannot access the Request object (thus neither the
Request.ApplicationPath) at design-time, so I can't even get a valid
path at design-time anyways.

Therefore, I would like to use an embedded resource (an image included
in the Visual Studio project, with 'Build Action' marked as "Embedded
Resource") at runtime.

But from what I can tell, System.Web.UI.Design.ControlDesigner only
allows me to really affect the HTML at design-time via
GetDesignTimeHtml(). But I cannot display an embedded resource with
HTML...

You can check to see if you are in design-time or not and set the
width/height in CreateChildControls

Mythran

 

[Justin]

As I said in the original message, " I have tried putting "image.Width
= Unit.Pixel(16); image.Height =
Unit.Pixel(16);" in CreateChildControls(), but that means that only
16x16 images can be used, because this affects _both_ design-time and
run-time. "

Unfortunately, that is not too good because that means the image will
always be forced to 16x16.

Thank you.

 

[Mythran]

As I said in the original message, " I have tried putting "image.Width
= Unit.Pixel(16); image.Height =
Unit.Pixel(16);" in CreateChildControls(), but that means that only
16x16 images can be used, because this affects _both_ design-time and
run-time. "

Unfortunately, that is not too good because that means the image will
always be forced to 16x16.

Thank you.

Yes, you did...and I said to check for design time in CreateChildControls
and wrap the code for changing the size with the check. That way, when it
renders during run-time, the code for changing the size is not ran.

Hope this helps,

Mythran

 

[Justin]

I mis-read, I apologize.

The only way I can think of to check for design-time is inelegant,
i.e., checking for the existence of a Context object. Do you know a
different way?

Also, I assume you have no idea how to render an image at design-time?

Thanks.

 

[Mythran]

I mis-read, I apologize.

The only way I can think of to check for design-time is inelegant,
i.e., checking for the existence of a Context object. Do you know a
different way?

Also, I assume you have no idea how to render an image at design-time?

Thanks.

You render an image the same way you render one at run-time (anchor
tag)...but the path to the image has to be valid in design-time as well.

VB.Net:

Private ReadOnly Property IsDesignTime() As Boolean
Get
Return (Not Me.Site Is Nothing) AndAlso Me.Site.DesignMode
End Get
End Property

C#:

private bool IsDesignTime
{
get {
return this.Site != null && this.Site.DesignMode;
}
}

hth

Mythran

 

[Michael Baltic]

I posted an answer in the other forum.

direct email:
userid = Michael.Baltic
server = NCMC.com
--
Staff Consultant II
Enterprise Web Services
Cardinal Solutions Group

Future Business Model
Loan Origination Services
National City Mortgage

 

[Justin]

You render an image the same way you render one at run-time (anchor
tag)...but the path to the image has to be valid in design-time as
well.

Yes, but I know of no way to get the project path at design-time**, and
I do not want to bundle an image with my webcontrol DLL.

this.Site.DesignMode

Thanks, that is the magical property I was hoping for.

Justin

**Actually, I know of a convoluted way to get the project path at
design time: use the EnvDTE library (this is my last resort). See this
link:
http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=1960&lngWId=10

 

[Justin]

Thank you, I replied to it. I'm not exactly sure what your suggestion
was.

Justin

 

[Justin]

You render an image the same way you render one at run-time (anchor
tag)...but the path to the image has to be valid in design-time as
well

Yes, but I know of no way to get the project path at design-time**, and

I do not want to bundle an image with my webcontrol DLL.

My original question was how to render an image in an ASP.NET
webcontrol from an embedded resource, which means, I infer, a stream.
But System.Web.UI.WebControls.Image has no way of consuming a stream.
This is my main question -- how to display an embedded image in a
webcontrol at design-time? Do I *have* to write the embedded image to
the filesystem, then pass that path to the Image.ImageUrl ?

Thank you,
Justin

 

[Michael Baltic]

Check the other forum for my latest response. Basically, web controls
shouldn't have the image embedded into the dll. As a general rule all of the
resources associated with the control should be able to be modified by the
site adminstrator.

A truly extensible control, should have the ability for the user to replace
the associated images and scripts with their own resources without
recompiling the control.
--
Direct Email: Michael.Baltic@RemoveCharactersUpTo#NCMC.Com

Staff Consultant II
Enterprise Web Services
Cardinal Solutions Group

 

[Mythran]

tag)...but the path to the image has to be valid in design-time as
well

I do not want to bundle an image with my webcontrol DLL.

My original question was how to render an image in an ASP.NET
webcontrol from an embedded resource, which means, I infer, a stream.
But System.Web.UI.WebControls.Image has no way of consuming a stream.
This is my main question -- how to display an embedded image in a
webcontrol at design-time? Do I *have* to write the embedded image to
the filesystem, then pass that path to the Image.ImageUrl ?

Thank you,
Justin

Yes, you can embed an image without writing the image to the filesystem (in
order for the http handler to receive it). What you would do is create a
class that inherits from HttpModule to handle a specific url sent by the
client, then place the specific url as the img tag's src property. There
are examples on the net on how to stream an image. Pull the image from the
assembly manifest as a Stream using the System.Reflection namespace.
(GetAssemblyResourceManifest or something, can't remember the exact name of
the method of the Assembly class to use).

HTH!

Mythran

 

[Justin]

Yes, that helps a lot. Thank you very much.

Justin