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How to inherit property values in a UserControl?

I have a page where I am adding a custom control like this:
<custom:ClickableIcon x:Name="DeleteTask" Grid.Column="2" Foreground="Red" Icon="Delete" Click="DeleteTask_Click" />
In my custom control, I have the following XAML:
<UserControl x:Name="clickableIconUserControl"
x:Class="Client.UWP.Controls.ClickableIcon"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Client.UWP.Controls" IsEnabledChanged="userControl_IsEnabledChanged">
<Grid x:Name="ohmygrid">
<SymbolIcon x:Name="CIIcon"
Foreground="{Binding Foreground, ElementName=clickableIconUserControl}"
Symbol="{Binding Icon, ElementName=clickableIconUserControl}"
Tapped="CIIcon_Tapped"/>
</Grid>
</UserControl>
This doesn't actually work. What I want is to copy the Foreground property for the control into specific places in the user control. I'd like to do this within a style sheet, direct property or whatever. In addition, I'd like to update the foreground when the foreground of the control on the page is changed.
Unfortunately, in this code (which is much simplified than the code I am actually trying to write), the Foreground is always #FF000000 in the debugger and I cannot seem to get a hold of the setting on the actual control to set it - either in code behind or as a binding.
How can I achieve this?

Is this concept of a button containing a textbox possible?

Recently I had been looking for a way to make the tabs in a TabControl editable and came across This example on telerik's website. That did exactly what I wanted but it got me thinking about a similar usage for buttons. I was wondering if it would be possible to use something like that and make a button that would show a textbox instead of the content presenter when say, you right click the button? I tried to make something like this work but so far have only ended up with a blank button.
<Button x:Name="SB" Height="222" Width="222" Click="SB_Click">
<ContentControl.ContentTemplate>
<DataTemplate>
<local:SuperButton Content="{Binding Path=x, Mode=TwoWay}"/>
</DataTemplate>
</ContentControl.ContentTemplate>
</Button>
Where x is a string variable and using the code behind from the link above (with a class name change, of course).
edit: This button will be in an itemscontrol, so I don't think naming the inner elements in xaml will work, but I do like the ease of Wolfgang's answer.

The WPF Content Model is really flexible and allows literally anything inside anything.
This is perfectly valid XAML:
<Button>
<TextBox/>
</Button>
Or even:
<Button>
<MediaElement Source="C:\Videos\WildLife.wmv"/>
</Button>

You can simply host a (e.g.) label (TextBlock) with the text AND a TextBox inside the Button and set their Visiblity properties.
That way, if you right click the button, the TextBox shows up.
<Button>
<Grid>
<TextBox Text=normal button caption" x:Name="label" />
<TextBox
x:Name="textbox"
Text="visible on right click"
MouseRightButtonDown="HandleRightClick"/>
</Grid>
</Button>
And then in your C# code create an event handler to set the Visiblity correctly.
void HandleRightClick(object sender, MouseButtonEventArgs e)
{
label.Visibility = Visibility.Collapsed;
textBlock.Visibility = Visibility.Visible;
}

Letting layout controls appear in a UserControl

I am trying to write a UserControl that will allow both single controls in it (like Label), as well as "layout" controls like StackPanel and friends.
I am having trouble doing that. The code I have works for single controls, but not for layout controls. I have a feeling this is an obvious fix, I am new to WPF. Here is the UserControl XAML:
<UserControl <!-- namespaces omitted for brevity -->>
<UserControl.ContentTemplate>
<DataTemplate>
<ContentPresenter Content="{TemplateBinding Content}" />
</DataTemplate>
</UserControl.ContentTemplate>
</UserControl>
When I try to use it like this:
<my:SpecialUserControl>
hello
</my:SpecialUserControl>
It's fine. But when I try to do something like
<my:SpecialUserControl>
<StackPanel>
<!-- stuff -->
</StackPanel>
</my:SpecialUserControl>
I get an error in Visual Studio Intellisense saying
The specified value cannot be assigned to the collection. The following type was expected: UIElement
And when I run the app (it builds), I get this exception at that place in the XAML:
'Add value to collection of type System.Windows.Controls.UIElementCollection threw an exception.' Line number x and line position y.
What can I do to make my UserControl able to accept any type of content?

The ContentPresenter should be a part of the ControlTemplate (<UserControl.Template>) of your control, not inside your ContentTemplate. I think that could be your problem.

Inherit your UserControl from ContentControl. ContentControl already has Content property combined with ContentPresenter inside ControlTemplate.
You can also use microsoft blend to get ContentControls visual tree.

AutoCompleteBox in silverlight toolkit for windows phone wrong display

I'm having a problem with the autocompletebox from the toolkit for windows phone. I bind it to some data, then when i press it and start typing, it discovers some items but they are displayed wrong (the list is shown separated from the box, and also if i click on any item, nothing happens. If i click where the item would be supposed to be (for example, right on the top of the box), then it gets selected. It looks like a rendering problem (bug?)) but perhaps i'm doing something wrong. Here's the code for the box :
<DataTemplate x:Key="DataTemplate1">
<ContentControl Content="{Binding Name}" Margin="8,7"/>
</DataTemplate>
<toolkit:AutoCompleteBox ItemsSource="{Binding}" x:Name="txtSelectValues" MinWidth="250" Margin="0,0,0,0" ItemTemplate="{StaticResource DataTemplate1}" VerticalAlignment="Top" />

Found it. It's a bug with the AutoCompleteBox. When inside a scrollviewer control, the dropdown gets messed up and displayed in an incorrect position

Its not just that is also to do with being placed inside of a Pivot/Panaroma as well as the scrollviewer, the silverlight gurus have stated they haven't a timeline for the fix for the Pivot control, and there is a nasty hack
http://silverlight.codeplex.com/workitem/7574

I think the answer might just be that you shouldn't be using a ContentControl directly used like this. Try using something like a TextBlock instead - e.g.:
<DataTemplate x:Key="DataTemplate1">
<TextBlock Text="{Binding Name}" Margin="8,7"/>
</DataTemplate>
If that's not the answer, then try pulling back to a simple example - especially removing all the Margin's, Width's, Alignment's, etc - then put them back in one-by-one to work out and understand what is causing the effect you are seeing.

Binding with a converter inside a template

I have defined a DataTemplate for a ListBox. Inside the template, I use TextBlock controls to display the properties of the data context. For example:
<TextBlock Text="{Binding Path=FirstName}" />
And if I do this:
<TextBlock Visibility="{Binding Path=IsAccountValid}" />
...the application runs, but there is a warning in the output about trying to bind a boolean property to a Visibility enumeration.
If I do this:
<TextBlock Visibility="{Binding Path=IsAccountValid,Converter={StaticResource visibilityOfBool}}" />
and somewhere in my App.xaml is:
<BooleanToVisibilityConverter x:Key="visibilityOfBool" />
I get a null reference exception.
I suspected this might be because the property IsAccountValid is not a dependency property, so I added a CheckBox to the window, and did this:
<TextBlock Visibility="{Binding Path=IsChecked,Converter={StaticResource visibilityOfBool},ElementName=butA}" />
But got the same error.
Why? The DataContext object is valid because if I bind IsAccountValid to the Text property, the value is correctly displayed.
The converter is never called, so I am wondering if it is the converter that cannot be found.
Why can the converter not be found? Why can the converter be found outside the data template and not inside the data template?
I tried building the template again with Blend, as Blend usually gets it right, but the code it generated was the same as mine.
I tried some of the fixes suggested on this website, including setting RelativeSource to TemplateParent and Self, but it made no difference.
What is going on?

We use such converter all the time in our Data Templates. Do you define the converter key inside your resource dictionary? Merge another Resource Dictionary?

The IsAccountValid property doesn't have to be a dependency property. If the converter couldn't be found then you wouldn't be able to open the form. You have the right approach using the converter but it is difficult to say exactly what is causing the exception without seeing more information.

As Amittai and Chris pointed out, it seems that you're headed in the right direction. I know it sounds a bit stupid, but try to add a space between the comma and the Converter= statement in the binding. Like so:
<TextBlock Visibility="{Binding Path=IsAccountValid, Converter={StaticResource visibilityOfBool}}" />
On some systems there are weird symptoms when there's no space after the comma. I couldn't find the actual reason for that.

Thank you all for your help in my investigation.
I have solved the problem.
These two lines of code are included in the DataTemplate, one is a TextBlock, and one is a hyperlink:
<TextBlock Text="Hello" Visibility="{Binding IsChecked,ElementName=chkBox,Converter={StaticResource visibilityOfBool}}" />
and
<TextBlock Grid.Column="1" >
<Hyperlink Click="ProgHomePageHyperlink_Click" >
<TextBlock Text="{Binding Path=Title}" />
</Hyperlink>
</TextBlock>
When they are both included in the code, the runtime throws a null reference exception.
But if I comment one of them out, either the TextBlock or the HyperLink, everything runs ok.
If I remove the Click handler from the hyperlink, everything runs ok.
If I comment out the converter in the TextBlock, the application runs, but I get a mismatched binding warning, which is well deserved.
So, including a Click handler in the hyperlink means the converter in the TextBlock cannot be found.
How weird is that!