Develop Reference

Problem accessing usercontrol in different contentplaceholder from another usercontrol

Now I know this does not make for good design practice, however it is legacy code with a bug that needs fixing so I am going to have to live with it.
The scenario is I have a set of nest Master pages (3 deep), call them Base > Template > 2Col. I am working at the 2Col level. As the name suggests the 2Col master page has two content placeholders, MainContent and SideContent.
I have user UserControl in MainContent that needs to reference another UserControl in SideContent.
ContentPlaceHolder ph = (ContentPlaceHolder)this.Page.Master.FindControl("SideContent");
MyUserControl uc = (MyUserControl )ph.FindControl("MyUserControl1");
I am not sure why this doesn't work, the intellisense when I debug would lead me to think that the ContentPlaceHolder is there, but the first line always returns null?
Thanks in advance!

Because of the nesting of Master pages you need access the correct master page like so:
ContentPlaceHolder ph = (ContentPlaceHolder)Parent.Parent.FindControl("SideContent");
Alternatively if you need to find any control on the Page from the Master use the following:
ContentPlaceHolder ph = (ContentPlaceHolder)FindControl(Page.Master, "SideContent");
...
private Control FindControl(Control parent, string id)
{
foreach (Control child in parent.Controls)
{
string childId = string.Empty;
if (child.ID != null)
{
childId = child.ID;
}
if (childId.ToLower() == id.ToLower())
{
return child;
}
else
{
if (child.HasControls())
{
Control response = FindControl(child, id);
if (response != null)
return response;
}
}
}
return null;
}

How call GetWebResourceUrl() when Page is null ?

I built custom ASP.NET control and it's working fine when I add it manually (drag and drop) or by code to controls in markup.
The custom control, MsgBox, had resources like JavaScript, CSS and images embedded in and the problem appeared when I tried to Render the control in class to return its HTML code, the Page instance is null and the "GetWebResourceUrl" needs it:
Page.ClientScript.GetWebResourceUrl(.....)
is there any way to get the resourceurl ? Here is my render code:
protected override void RenderContents(HtmlTextWriter writer)
{
using (PlaceHolder plh = new PlaceHolder())
{
if (Page != null)
{
if (DesignMode || Page.Header == null)
RegisterCSSInclude(plh);
}
HtmlGenericControl container = new HtmlGenericControl("div");
container.EnableViewState = false;
container.InnerHtml = "Control html code";
plh.Controls.Add(container);
plh.RenderControl(writer);
}
}
RegisterCSSInclude is method to register my css files:
private void RegisterCSSInclude(Control target)
{
// CSS
bool linkIncluded = false;
foreach (Control c in target.Controls)
{
if (c.ID == "MsgBxStyle")
{
linkIncluded = true;
}
}
if (!linkIncluded)
{
HtmlGenericControl globalCsslink = new HtmlGenericControl("link");
globalCsslink.ID = "MsgBxGStyle";
globalCsslink.Attributes.Add("href", Page.ClientScript.GetWebResourceUrl(typeof(MessageBoxCtrl), "MessageBox.MsgBxStyles.WeDevMsgBox.css"));
globalCsslink.Attributes.Add("type", "text/css");
globalCsslink.Attributes.Add("rel", "stylesheet");
globalCsslink.EnableViewState = false;
target.Controls.Add(globalCsslink);
HtmlGenericControl csslink = new HtmlGenericControl("link");
csslink.ID = "MsgBxStyle";
csslink.Attributes.Add("href", Page.ClientScript.GetWebResourceUrl(typeof(MessageBoxCtrl), "MessageBox.MsgBxStyles." + Style.ToString().ToLower() + ".css"));
csslink.Attributes.Add("type", "text/css");
csslink.Attributes.Add("rel", "stylesheet");
csslink.EnableViewState = false;
target.Controls.Add(csslink);
}
}
Update:
PS: I'm tring to use control in generic handler (ashx) where I call ShowMsgBox method which is a method in a class and not in a page or user control.
ShowMsgBox method should create an instance of MsgBox control and render it then return the html code to ashx class :
var htmlCode = MyClass.ShowMsgBox("myMsg");
context.Response.write(htmlCode);

I built a custom ASP.NET control ...
I'm tring to use control in generic handler (ashx) ... not in a page or user control.
A Page is a handler. You want to use a convenience provided by the Page class, but you don't want to inherit from Page. The niceties of Page, such as ClientScript, expect a Page from which to get various information.
You can provide a dummy Page object to your control by setting the Page property of your custom Control:
this.Page = new Page();
...then you will need to set various properties (assuming they are public) which are expected by ClientScriptManager.GetWebResourceUrl():
this.Page.Foo = "bar";
then you can call:
this.Page.ClientScript.GetWebResourceUrl(...);

If this is the specific class that inherits from WebControl page shouldn't be null. If its another class that you are rendering as part of a hierarchy you can add a parameter of type Page and pass the reference of the current page to it.

ASP.NET How to access a deeply nested user control on the parent page

I have a login control and at is nested 2 deep in a header control
i.e Page --> Header Control --> Login Control. I cannot get a reference to the control on the page using FindControl. I want to be able to set the visible property of the control like
if (_loginControl != null)
_loginControl.Visible = false;
I ended up using a recursive FindControl method to find the nested control.
public static Control FindControlRecursive(Control root, string id)
{
if (root.ID == id)
{
return root;
}
foreach (Control c in root.Controls)
{
Control t = FindControlRecursive(c, id);
if (t != null)
{
return t;
}
}
return null;
}

Are you needing to disable/hide the User Control from the ASP.NET page it resides on (or does the User Control exist on a master page, say)? If it's in the same page, then in your ASP.NET page's code-behind you'd do:
MyUserControlsID.Visible = false
Where MyUserControl is the ID of your User Control. To determine the ID of your User Control look at the markup of your .aspx page and you will see something like this:
<uc1:UserControlName ID="MyUserControlsID" runat="server" ... />
Happy Programming!

A good way would be to use:
Page.FindControl()
if that yields null, the control is not there.

Try calling this.FindControl("_loginControl") or this.Page.FindControl("_loginControl").
See MSDN for method details:
http://msdn.microsoft.com/en-us/library/system.web.ui.control.findcontrol.aspx

The login control, if it's registered in the markup, will also be an instance member of your codebehind page; you can refer to it from the codebehind class as if it were a normal member, using the same name you provided as the ID (I do recommend using codebehinds for most logic, instead of inlining code in the markup, BTW).
You can also use the FindControl() method of your page, which will search its control subtree for a control with a given ID. That takes longer, so I would recommend the first option unless the logic control is added dynamically and you don't always know it's there.

private List<Control> GetAllNestedUserControl(Control ph)
{
List<Control> Get = new List<Control>();
foreach (var control in ph.Controls)
{
if (control is UserControl)
{
UserControl uc = control as UserControl;
if (uc.HasControls())
{
Get = GetAllNestedUserControl(uc);
}
}
else
{
Control c = (Control)control;
if (!(control is LiteralControl))
{
Get.Add(c);
}
}
}
return Get;
}
just call this code from you any parent page and then get any control by the following code
List<Control> Get = GetAllNestedUserControl(ph);
Label l = (Label)Get.Find(o => o.ID == "lblusername");
l.Text = "changed from master";

Change panel "visible" property on MasterPage from Child pages

I want to show some panel with a label, both located on a MasterPage, from inside it's child pages.. I already did the coding on the MasterPage:
public class MyMaster : MasterPage
{
public void ShowPanel(string pMessage)
{
labelInside.Text = pMessage;
myPanel.visible = true;
}
}
Then I make the calls from child pages:
public void ShowPanel(string pMessage)
{
MyMaster masterPage = this.Master as MyMaster;
masterPage.ShowPanel(pMessage);
}
This "works" ok, but it won't show nothing, since I need the page to be "refreshed" in an "ajax-way" like an UpdatePanel, which I can't use because the Trigger is in another page, right?
I really need this to work.. even if you have another completely different way to do this, I would appreciate.

You must place your panel inside an UpdatePanel(UpdateMode conditional) and in ShowPanel call its Update method.

Have you considered having the masterpage just have a placeholder for the label, but having each child page put its own content label inside that placeholder, which it would then have full control over?

you can subClass your page, and expose a property say.. MyPage.FooVisible
than in your masterPage, you can:
myPage = this.Page as MyPage
if (myPage != null) myPage.FooVisble = false;
in your page you can handle that any way you like,
FooVisible {
set { SomeElement.Visible = value; }
}
pseudo code of course :)

Dynamically adding Content blocks to Masterpage fails after Master.FindControl

I've encountered an odd problem that doesn't make any sense to me. I am trying to dynamically set up MasterPage Content controls on a page. I have it working nicely with the following code:
protected override void OnPreInit(EventArgs e)
{
base.OnPreInit(e);
MasterPageFile = "~/MasterPages/Default.master";
string existantContentPlaceHolderID = "ContentPlaceHolder1";
string nonExistantContentPlaceHolderID = "foo";
//Control c = Master.FindControl(existantContentPlaceHolderID);
//Control c1 = Master.FindControl(nonExistantContentPlaceHolderID);
TextBox t = new TextBox
{
Text = "Text"
};
ITemplate iTemplate = new GenericITemplate(container => container.Controls.Add(t));
AddContentTemplate(existantContentPlaceHolderID, iTemplate);
}
public delegate void InstantiateTemplateDelegate(Control container);
public class GenericITemplate : ITemplate
{
private readonly InstantiateTemplateDelegate m_instantiateTemplate;
public void InstantiateIn(Control container)
{
m_instantiateTemplate(container);
}
public GenericITemplate(InstantiateTemplateDelegate instantiateTemplate)
{
m_instantiateTemplate = instantiateTemplate;
}
}
This works great, except I want to be able to double-check that the contentPlaceHolderIDs exist on the MasterPage before calling AddContentTemplate as the Page will throw an error if you add a Content control that points to a non-existing ContentPlaceHolder.
The problem I am having is that in the above example when I call one of the commented Master.FindControl lines, the TextBox no longer renders.
Does anyone have any ideas why this might be... I cannot makes heads or tails of what is going on.
Thanks,
Max

The problem is that AddContentTemplate just records its parameters in a hashtable ready to be combined with the master page instance when it is created. Calling it after the master page has been created won't do anything, and reading the Master property causes the master page to be created.
The best way I can see around this is to create a separate instance of the master page with LoadControl, which you can inspect without affecting the page's own Master property...
MasterPage testMaster = (MasterPage) LoadControl( MasterPageFile );
Control c = testMaster.FindControl(existantContentPlaceHolderID);
There's some overhead in creating a second instance, but it's not immediately obvious to me whether it will be worth worrying about.