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How do I access controls from the parent page from within an ASP.NET User Control?

I have an ASP.NET Web Forms page childPage.aspx with masterPage.aspx as the master page. The childPage.aspx has a user control (userControl.ascx) control defined on it. Now, I am trying to access the controls on childPage.aspx from within the user control. I have tried a handful of different approaches:
HtmlContainerControl ProductMenu = (HtmlContainerControl)Page.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)this.Page.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)Parent.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)this.Parent.parent.FindControl("ContaintHolder").FindControl("ProductMenu")
In above code, ProductMenu is the id of the <div runat="server" /> on childPage.aspx. Now, I am trying to access it from within my user control, but that fails to return the div.
Please help me out. How should I do this? Thanks in advance.

The reason this doesn't work is likely because the FindControl() method is not recursive. This is called out in the MSDN documentation:
This method will find a control only if the control is directly contained by the specified container; that is, the method does not search throughout a hierarchy of controls within controls.
So, for instance, Page.FindControls() will only search for controls listed in the Page.Controls collection; it won't search the Controls collection of each of those controls. As such, Page.FindControl() would only work if the ProductMenu were at the top-level of your ASPX page; if it is instead nested within, for instance, a Panel control then this code won't work.
To resolve this, you'll need to write a recursive function to crawl the control tree. For instance:
public Control FindControl(Control parentControl, string controlName) {
foreach (var childControl in parentControl.Controls) {
if (childControl.Id == controlName) return childControl;
var foundControl = FindControl(childControl, controlName);
if (foundControl != null) return childControl;
}
return null;
}
In your case, assuming you'll always be looking for an instance of an HtmlContainerControl, you could even validate the type and return a strongly typed object, should you choose. That said, if you want to keep it strongly typed while still supporting different types, you could instead use a generic:
public T FindControl<T>(Control parentControl, string controlName) where T : Control {
foreach (var childControl in parentControl.Controls) {
if (childControl.Id == controlName) return childControl;
var foundControl = FindControl<T>(childControl, controlName);
if (foundControl != null && foundControl is T) return childControl;
}
return null;
}
In addition, if you'll need to do this repeatedly, you might add this as an extension method to the Page class so it's easily accessible on multiple pages.

Loop through all controls of a Form, even those in GroupBoxes

I'd like to add an event to all TextBoxes on my Form:
foreach (Control C in this.Controls)
{
if (C.GetType() == typeof(System.Windows.Forms.TextBox))
{
C.TextChanged += new EventHandler(C_TextChanged);
}
}
The problem is that they are stored in several GroupBoxes and my loop doesn't see them. I could loop through controls of each GroupBox individually but is it possible to do it all in a simple way in one loop?

The Controls collection of Forms and container controls contains only the immediate children. In order to get all the controls, you need to traverse the controls tree and to apply this operation recursively
private void AddTextChangedHandler(Control parent)
{
foreach (Control c in parent.Controls)
{
if (c.GetType() == typeof(TextBox)) {
c.TextChanged += new EventHandler(C_TextChanged);
} else {
AddTextChangedHandler(c);
}
}
}
Note: The form derives (indirectly) from Control as well and all controls have a Controls collection. So you can call the method like this in your form:
AddTextChangedHandler(this);
A more general solution would be to create an extension method that applies an action recursively to all controls. In a static class (e.g. WinFormsExtensions) add this method:
public static void ForAllControls(this Control parent, Action<Control> action)
{
foreach (Control c in parent.Controls) {
action(c);
ForAllControls(c, action);
}
}
The static classes namespace must be "visible", i.e., add an appropriate using declaration if it is in another namespace.
Then you can call it like this, where this is the form; you can also replace this by a form or control variable whose nested controls have to be affected:
this.ForAllControls(c =>
{
if (c.GetType() == typeof(TextBox)) {
c.TextChanged += C_TextChanged;
}
});

A few simple, general purpose tools make this problem very straightforward. We can create a simple method that will traverse an entire control's tree, returning a sequence of all of it's children, all of their children, and so on, covering all controls, not just to a fixed depth. We could use recursion, but by avoiding recursion it will perform better.
public static IEnumerable<Control> GetAllChildren(this Control root)
{
var stack = new Stack<Control>();
stack.Push(root);
while (stack.Any())
{
var next = stack.Pop();
foreach (Control child in next.Controls)
stack.Push(child);
yield return next;
}
}
Using this we can get all of the children, filter out those of the type we need, and then attach the handler very easily:
foreach(var textbox in GetAllChildren().OfType<Textbox>())
textbox.TextChanged += C_TextChanged;

Try this
AllSubControls(this).OfType<TextBox>().ToList()
.ForEach(o => o.TextChanged += C_TextChanged);
where AllSubControls is
private static IEnumerable<Control> AllSubControls(Control control)
=> Enumerable.Repeat(control, 1)
.Union(control.Controls.OfType<Control>()
.SelectMany(AllSubControls)
);
LINQ is great!

Haven't seen anyone using linq and/or yield so here goes:
public static class UtilitiesX {
public static IEnumerable<Control> GetEntireControlsTree(this Control rootControl)
{
yield return rootControl;
foreach (var childControl in rootControl.Controls.Cast<Control>().SelectMany(x => x.GetEntireControlsTree()))
{
yield return childControl;
}
}
public static void ForEach<T>(this IEnumerable<T> en, Action<T> action)
{
foreach (var obj in en) action(obj);
}
}
You may then use it to your heart's desire:
someControl.GetEntireControlsTree().OfType<TextBox>().ForEach(x => x.Click += someHandler);

As you have stated, you will have to go deeper than just cycling over each element in your form. This, unfortunately, implies the use of a nested loop.
In the first loop, cycle through each element. IF the element is of type GroupBox, then you know you'll need to cycle through each element inside the groupbox, before continuing; else add the event as normal.
You seem to have a decent grasp of C# so I won't give you any code; purely to ensure you develop all the important concepts that are involved in problem solving :)

you can only loop through open forms in windows forms using form collection for example to set windows start position for all open forms:
public static void setStartPosition()
{
FormCollection fc = Application.OpenForms;
foreach(Form f in fc)
{
f.StartPosition = FormStartPosition.CenterScreen;
}
}

I know that this is an older topic, but would say the code snippet from http://backstreet.ch/coding/code-snippets/mit-c-rekursiv-durch-form-controls-loopen/ is a clever solution for this problem.
It uses an extension method for ControlCollection.
public static void ApplyToAll<T>(this Control.ControlCollection controlCollection, string tagFilter, Action action)
{
foreach (Control control in controlCollection)
{
if (!string.IsNullOrEmpty(tagFilter))
{
if (control.Tag == null)
{
control.Tag = "";
}
if (!string.IsNullOrEmpty(tagFilter) && control.Tag.ToString() == tagFilter && control is T)
{
action(control);
}
}
else
{
if (control is T)
{
action(control);
}
}
if (control.Controls != null && control.Controls.Count > 0)
{
ApplyToAll(control.Controls, tagFilter, action);
}
}
}
Now, to assign an event to all the TextBox controls you can write a statement like (where 'this' is the form):
this.Controls.ApplyToAll<TextBox>("", control =>
{
control.TextChanged += SomeEvent
});
Optionally you can filter the controls by their tags.

Since the Question regarding "Adding an Event to your TextBoxes"; was already answered; I'm providing some explanation and adding an iteration alternative using a for loop instead.
Problem:
Being Unable to Get Controls Inside a Container.
Solution:
In order to retrieve the Controls inside a Container you have to specify the Container that Contains the Controls you wish to access to.
Therefore your loop must check the Controls inside a Container.
Otherwise your loop will not find the Controls inside a Container.
i.e:
foreach (Control control in myContainer.Controls)
{
if (control is TextBox) { /* Do Something */ }
}
In case you have several Containers:
Initially iterate the Containers.
Then iterate over the controls inside the container (the container found in the initial iteration).
Pseudo Code Example on How to use a for Loop Instead:
/// <summary> Iterate Controls Inside a Container using a for Loop. </summary>
public void IterateOverControlsIncontainer()
{
// Iterate Controls Inside a Container (i.e: a Panel Container)
for (int i = 0; i < myContainer.Controls.Count; i++)
{
// Get Container Control by Current Iteration Index
// Note:
// You don't need to dispose or set a variable to null.
// The ".NET" GabageCollector (GC); will clear up any unreferenced classes when a method ends in it's own time.
Control control = myContainer.Controls[i];
// Perform your Comparison
if (control is TextBox)
{
// Control Iteration Test.
// Shall Display a MessageBox for Each Matching Control in Specified Container.
MessageBox.Show("Control Name: " + control.Name);
}
}
}

Updated answer:
I needed to disable all the controls in a form, including groupboxes. This code worked:
private void AlterControlsEnable(bool ControlEnabled)
{
foreach (Control i in Controls)
i.Enabled = ControlEnabled;
}

find properties that has an attribute in a control

I have a page with a number of controls.
As the page is rendering I want to loop through all controls on the page and find any control that has a property with certain attribute. I am attempting to do this with c# - any ideas how I might achieve this?

I dont know how big is your control tree. This is what I would do. I'm not promissing the best performance.
Case 1. Looking for .NET Attributes
IEnumerable<Control> GetMarkedControls(ControlCollection controls)
{
foreach(Control c in controls)
{
var props = c.GetType().Properties();
if(props.Count(x => x.GetCustomAttributes(false).OfType<YourAttribute>().Count() > 0) > 0)
yield return c;
foreach (Control ic in GetMarkedControls(c.Controls))
yield return ic;
}
}
Case 2. Looking for HTML attributes
IEnumerable<WebControl> GetMarkedControls(ControlCollection controls)
{
foreach(Control c in controls)
{
if(c is WebControl)
{
var wc = c as WebControl;
if (wc.Attributes.FirstOrDeafult(x => x.Name == "yourAttribute") != null)
yield return c;
}
foreach (Control ic in GetMarkedControls(c.Controls))
yield return ic;
}
}
Now you can call it this way: var controlsWAttribute = GetMarkedControls(this.Controls); from your page or any control. This way you are not forced to call it at the page level.
With this method you explore the whole control tree in your page or control recursively.

You need to use Reflection
http://msdn.microsoft.com/en-us/library/system.reflection.aspx
using reflection you can get all the attributes of an object

Every control that is on the page has a "controls" property which contains all of its children controls. I have written recursive functions to loop through these before but do not have any on hand. Let me try to write one real quick:
public Collection<Control> findControlsWithAttributes(Control startingControl)
{
Collection<Control> toReturn = new Collection<Control>();
foreach (Control curControl in startingControl.controls)
{
if (DO COMPARISON HERE WITH CURCONTROL) toReturn.add(curControl);
if (curControl.Count() > 0) findControlsWithAttributes(curControl, toReturn);
}
return toReturn;
}
private void findControlsWithAttributes(Control startingControl, Collection<Control> inputCollection)
{
foreach (Control curControl in startingControl.controls)
{
if (DO COMPARISON HERE WITH CURCONTROL) inputCollection.add(curControl);
if (curControl.Count() > 0) findControlsWithAttributes(Control startingControl, Collection<Control> inputCollection);
}
}
Its been a little while since i've done this and I can't remember off the top of my head if Collection.Count is a method or property so make sure you check that first, but if you pass the page in then this will check against every server-visible control on your page and return a collection containing controls that match your comparison.
Lastly, Control.Attributes will return an AttributeCollection which you should be able to subsequently compare against.

Not sure what attributes you are after but if class attributes is what you are after look to #user751975 other wise you can do something like ...
page.Controls.Cast<System.Web.UI.WebControls.WebControl>().First().Attributes["class"]

Find ContentPlaceHolders in Master page

I'm looking for a way to dynamically load a master page in order to get a collection of ContentPlaceHolders within.
I would prefer not to have to load a page object to assign the master page to before I can access it's controls, but if that's the only way I'll be happy to use it. This is the way I was hoping it would work:
Page page = new Page();
page.MasterPageFile = "~/home.master";
foreach (Control control in page.Master.Controls)
{
if (control.GetType() == typeof(ContentPlaceHolder))
{
// add placeholder id to collection
}
}
But page.Master throws a null reference exception. It only seems to load at some point when an actual page has been created in the page lifecycle.
I even thought of dynamically changing the current page's MasterPageFile on Page_Init(), reading all ContentPlaceHolders then assigning the original MasterPageFile back, but that would be horrible!
Is there a way to load a master page into memory independent of an actual page so that I can access properties of it?
My final resort will probably involve parsing the master page contents for ContentPlaceHolders instead, which isn't as elegant but might be a bit faster.
Anyone able to help please? Many thanks.

You should be able to use LoadControl to load the master page an enumerate the Controls collection.
var site1Master = LoadControl("Site1.Master");
To find the Content Controls you will need to recursively search the Controls collection. Here is a quick and dirty example.
static class WebHelper
{
public static IList<T> FindControlsByType<T>(Control root)
where T : Control
{
List<T> controls = new List<T>();
FindControlsByType<T>(root, controls);
return controls;
}
private static void FindControlsByType<T>(Control root, IList<T> controls)
where T : Control
{
foreach (Control control in root.Controls)
{
if (control is T)
{
controls.Add(control as T);
}
if (control.Controls.Count > 0)
{
FindControlsByType<T>(control, controls);
}
}
}
}
The above can be used as follows
// Load the Master Page
var site1Master = LoadControl("Site1.Master");
// Find the list of ContentPlaceHolder controls
var controls = WebHelper.FindControlsByType<ContentPlaceHolder>(site1Master);
// Do something with each control that was found
foreach (var control in controls)
{
Response.Write(control.ClientID);
Response.Write("<br />");
}

foreach Control ctrl in SomePanel.Controls does not get all controls

I have a panel with a bunch of labeles and textboxes inside of it.
The code:
foreach (Control ctrl in this.pnlSolutions.Controls)
Seems to only be finding html table inside the panel and 2 liternals.
But it does not get the textboxes that are in the html table.
Is there a simple way to get all the controls inside of a panel regardless of the nesting?
thanks!

Here's a lazy solution:
public IEnumerable<Control> GetAllControls(Control root) {
foreach (Control control in root.Controls) {
foreach (Control child in GetAllControls(control)) {
yield return child;
}
}
yield return root;
}
Remember also that some controls keep an internal collection of items (like the ToolStrip) and this will not enumerate those.

You would need to recursively "treewalk" through the controls, think about it like walking through a folder structure.
there is a sample Here

As far as I know your have to implement the recursion yourself, but its not really difficult.
A sketch (untested):
void AllControls(Control root, List<Control> accumulator)
{
accumulator.Add(root);
foreach(Control ctrl in root.Controls)
{
AllControls(ctrl, accumulator);
}
}

I had exactly the problem stated in the question so this may help somebody. I was attempting to clear a control collection prior to rewriting it.
private void clearCollection(Control.ControlCollection target)
{
foreach (Control Actrl in target)
{
if (Actrl is Label || Actrl is Button)
{
target.Remove(Actrl);
}
}
}
By removing the control inside the foreach loop it must mess with the internal pointers and the result is controls in the collection are missed.
My solution was to find all the controls then remove in a separate loop.
private void clearCollection(Control.ControlCollection target)
{
List<Control> accumulator = new List<Control>();
foreach (Control Actrl in target)
{
if (Actrl is Label || Actrl is Button)
{
accumulator.Add(Actrl); // find all controls first.
}
}
for (int i = 0; i < accumulator.Count; i++)
{
target.Remove(accumulator[i]);
}
}

The reason is because the only controls that are direct children of your panel are the table and the literals you mention, and it is only these that this.pnlSolutions.Controls returns.
The text boxes an labels are child controls of the table, making them grandchildren of the panel.
As #Yoda points out you need to recursively walk the controls to find them all.