Develop Reference

Add class to ASP.NET MasterPage control

This is the code in my MasterPage:
<li id="liABOUT" runat="server">ABOUT</li>
When I am on another page referencing the MasterPage I want to add a class to this li control, something like this. Cant get it to work. Using ASP.NET 4.5
Me.Master.FindControl("ContentPlaceHolderMaster").FindControl("LiAbout").Attributes.Add("class", "active")
VB.NET or C# Code would be fine

You can create a public property in your MasterPage :
public String LiAboutClass
{
get { return liABOUT.Attributes["class"]; }
set { liABOUT.Attributes["class"] = value; }
}
Access this property in your ContentPage:
var siteMaster = (SiteMaster)this.Master;
if (siteMaster != null) siteMaster.LiAboutClass = "active";
Edit: Also you can use MasterType. it allows you to access the MasterTypes properties directly.

This works for me. I first converted it to HtmlGenericControl and then added attribute.
(Master.FindControl("liABOUT") as HtmlGenericControl).Attributes.Add("class", "active");

This worked....
' Get reference to control located on master page
Dim lb As HtmlGenericControl = Page.Master.FindControl("liABOUT")
lb.Attributes.Add("class", "active")

Accessing property of root master page

I fell over the following exercise:
You got a masterpage "custom.master". You then have a nested masterpage
"nested.master". You then have a content page that uses the
nested.master. How do you access a property of custom.master from the
content page.
The right answer should be "parent.master.propertyname". But I would expect "master.master.propertyname" as the parent of a contentpage should not be a masterpage.
As everyone sais, "parent.master" is the right one I am probably wrong. Can anyone provide an explanaition or a link, why parent.master would be the right choice?

The following code will give you the desired result
this.Master.Master.PropertyName
Thanks,
Abhishek S.

I know this is an old question but I came across a need for doing this recently and thought I'd add my solution which works for any master page nesting level and also returns the master as your specific type so that you can access properties on it instead of just a System.Web.UI.MasterPage as this.Master.Master would give:
public static T GetRootMasterPage<T>(MasterPage master) where T : MasterPage
{
if (master != null)
{
if (master.Master == null) // We've found the root
{
if (master is T)
{
return master as T;
}
else
{
throw new Exception($"GetRootMasterPage<T>: Could not find MasterPage of type {typeof(T)}");
}
}
else // We're on a nested master
{
return GetRootMasterPage<T>(master.Master);
}
}
return null;
}
Usage:
var root = GetRootMasterPage<Root>(this.Master);
// ...
// Do whatever with your 'Root' master page type

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";

Finding controls inside nested master pages

I have a master page which is nested 2 levels. It has a master page, and that master page has a master page.
When I stick controls in a ContentPlaceHolder with the name "bcr" - I have to find the controls like so:
Label lblName =(Label)Master.Master.FindControl("bcr").FindControl("bcr").FindControl("Conditional1").FindControl("ctl03").FindControl("lblName");
Am I totally lost? Or is this how it needs to be done?
I am about to work with a MultiView, which is inside of a conditional content control. So if I want to change the view I have to get a reference to that control right? Getting that reference is going to be even nastier! Is there a better way?
Thanks

Finding controls is a pain, and I've been using this method which I got from the CodingHorror blog quite a while ago, with a single modification that returns null if an empty id is passed in.
/// <summary>
/// Recursive FindControl method, to search a control and all child
/// controls for a control with the specified ID.
/// </summary>
/// <returns>Control if found or null</returns>
public static Control FindControlRecursive(Control root, string id)
{
if (id == string.Empty)
return null;
if (root.ID == id)
return root;
foreach (Control c in root.Controls)
{
Control t = FindControlRecursive(c, id);
if (t != null)
{
return t;
}
}
return null;
}
In your case, I think you'd need the following:
Label lblName = (Label) FindControlRecursive(Page, "lblName");
Using this method is generally much more convenient, as you don't need to know exactly where the control resides to find it (assuming you know the ID, of course), though if you have nested controls with the same name, you'll probably get some strange behavior, so that might be something to watch out for.

Firstly, you should know that MasterPages actually sit inside Pages. So much so that a MasterPage's Load event is actually called after your ASPX's Load event.
This means, the Page object is actually the highest control in the control hierarchy.
So, knowing this, the best way to find any control in such a nested environment, is to write a recursive function that loops through every control and child controls until it finds the one you're looking for. in this case, your MasterPages are actually child controls of the main Page control.
You get to the main Page object from inside any control like this:
C#:
this.Page;
VB.NET
Me.Page
I find that usually, the Control's class FindControl() method is pretty useless, as the enviroment is always nested.
Because if this, I've decided to use .NET's 3.5 new Extension features to extend the Control class.
By using the code below (VB.NET), in say, your AppCode folder, all your controls will now peform a recursive find by calling FindByControlID()
Public Module ControlExtensions
<System.Runtime.CompilerServices.Extension()> _
Public Function FindControlByID(ByRef SourceControl As Control, ByRef ControlID As String) As Control
If Not String.IsNullOrEmpty(ControlID) Then
Return FindControlHelper(Of Control)(SourceControl.Controls, ControlID)
Else
Return Nothing
End If
End Function
Private Function FindControlHelper(Of GenericControlType)(ByVal ConCol As ControlCollection, ByRef ControlID As String) As Control
Dim RetControl As Control
For Each Con As Control In ConCol
If ControlID IsNot Nothing Then
If Con.ID = ControlID Then
Return Con
End If
Else
If TypeOf Con Is GenericControlType Then
Return Con
End If
End If
If Con.HasControls Then
If ControlID IsNot Nothing Then
RetControl = FindControlByID(Con, ControlID)
Else
RetControl = FindControlByType(Of GenericControlType)(Con)
End If
If RetControl IsNot Nothing Then
Return RetControl
End If
End If
Next
Return Nothing
End Function
End Module

Although I love recursion, and agree with andy and Mun, one other approach you may want to consider is to have a strongly typed Master page. All you have to do is add one directive in your aspx page.
Instead of accessing a page's control from your master page, consider accessing a control in your master page from the page itself. This approach makes a lot of sense when you have a header label on your master page, and want to set its value from each page that uses the master.
I'm not 100% sure, but I think this would be simpler technique with nested master pages, as you would just point the VirtualPath to the master containing the control you wish to access. It might prove to be tricky though if you want to access two controls, one in each respective master page.

Here is a code that is more generic and works with a custom condition (that can be a lambda expression!)
Call:
Control founded = parent.FindControl(c => c.ID == "youdId", true);
Control extension
public static class ControlExtensions
{
public static Control FindControl(this Control parent, Func<Control, bool> condition, bool recurse)
{
Control founded = null;
Func<Control, bool> search = null;
search = c => c != parent && condition(c) ? (founded = c) != null :
recurse ? c.Controls.FirstOrDefault(search) != null :
(founded = c.Controls.FirstOrDefault(condition)) != null;
search(parent);
return founded;
}
}

I have used the <%# MasterType VirtualPath="~/MyMaster.master" %> method. I have a property in the main master page then in the detail master page other property with the same name calling the main master property and it works fine.
I have this in the main master page
public string MensajeErrorString
{
set
{
if (value != string.Empty)
{
MensajeError.Visible = true;
MensajeError.InnerHtml = value;
}
else
MensajeError.Visible = false;
}
}
this is just a div element that have to show an error message. I would like to use this same property in the pages with the detail master page(this is nested with the main master).
Then in the detail master I have this
public string MensajeErrorString
{
set
{
Master.MensajeErrorString = value;
}
}
Im calling the main master property from the detail master to create the same behavior.

I just got it working perfectly.
In contentpage.aspx, I wrote the following:
If Master.Master.connectsession.IsConnected Then
my coded comes in here
End If