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How do you bind 2 controls?

In my app, there is a feature to customize it's own Controls (like Textbox, Labels, Textblocks, Buttons, etc), this feature interface is located inside a TabItem. Lets say i want to modify Button A, which is located in ANOTHER container. On the feature interface, i set it's Foreground property to White, at this moment i don't know whether the Button looks better or not, so i have to go to the container which contains that Button.
What am i trying to do is, i want to create a "preview" Control (which is the same type as the actual target) inside the feature interface. I want any changes on this "preview" control are reflected to the actual target Control. With this, i won't need to navigate to where the target Control located.
When i used the title ("How do you bind 2 controls)" with google, all results actually gives me "how to bind SINGLE property of a control to another control's property". What i want is how do you bind/link 2 Controls literally, i mean, i want to bind ALL properties of Control A to ALL properties of Control B.
Binding them one by one is one (tiring) way. Is there another way to achieve this?
I would prefer code-behind method.

There is no "fast" way to do this, you will have to bind one by one according to your buisness logic.
Also a binding is not cheap regarding performance so binding each and every property of a control even those you dont explicitly need, is a warning sign.

WPF: Create a UserControl or a CustomControl?

I'm not very clear of when to use a CustomControl and when to use an UserControl. I basically know what CustomControl allow(more customization when using with template).
I want to make a "File browse" control in WPF(TextBlock that displays the current path + Button that trigger a "Open File Dialog").
I'm not sure, because at some places I find that they say this should always "replace" a WPF control. I was more thinking that a a CustomControl was more like a way to display and edit one new semantic value (in my case, a "File(path)").
So, if we don't take into account which one is easier to do, what would be the more adequate between CustomControl and UserControl for the "FileBrowse" control that I'm speaking about?
Thank you

Custom Control:
A loosely coupled control w.r.t code and UI
Derives from Control
Defines UI in a ResourceDictionary
UI can be changed in different projects
Has full toolbox support
Defines a single control
More flexible
User Control :
A tightly coupled control w.r.t code and UI
Derives from UserControl
Defines UI as normal XAML
UI is fixed and can't have different looks in different project
Can't be added to the toolbox
Defines a set of controls
Not very flexible like a Custom Control
When we talk about differences, it is more important to emphasis on the context when to use what:
When you have a rapid and fixed content in your UI, use UserControl.
When you want to separate some basic functionality of your main view to some smaller pieces with reusability, use UserControl.
When you want to use your control in different projects and each project may want to change the look, use CustomControl.
When you want to implement some additional functionality for a control, create a CustomControl derived from the base control.
When you want to apply themes to your controls, use CustomControl.
When you want to add toolbox support for your control, so that your user will be able to do drag and drop to the designer, use CustomControl.

I think a UserControl is the one to choose, for it is used for a kind of "assembly of existing controls". In your case a button and a file open dialog. It will then get a specific look and feel (for example the default look of a button and the default look of a file open dialog).
The CustomControl is kind of the other way round. It has no look and feel by itself. It is completely abstract concerning layout. The layout comes into play, wwhen assigning a style to it.

In general a custom control extends an existing control while a user control creates a new control type from a collection of existing controls. I would say that a user control is better suited, based on the information you've given.

Why do we need UserControl ? It seams that a Custom Control can do all the things that UserControl can do. WPF & Windows Store App [duplicate]

I've been reading some explanations about the difference between User and Custom Controls, for example this:
http://www.wpftutorial.net/CustomVsUserControl.html
I want to create, for example, a simple composition of a datagrid with 2 comboboxes which are responsible to change the values from the datagrid's items. I want to create a specific control for this because I'm going to use it a lot of times. I would like to implement the logic behind and then in the xaml invocation I only have to specify the itemsSource.
For this example should I create a User or Custom control? Since I will have properties and logic, should I have a viewmodel for this control?
EDIT: Do you know some articles with clear conceptual separation between these 2 options?

Choice is not only between user control and custom control, but among user control, custom control, customizing control template, customizing data template, header template (for collection based controls), attached properties.
Refer to Control Authoring overview
I go by following order of consideration
Attached Properties : If functionality can be achieved, I use attached properties. Example, Numeric text box.
Control Template : When requirement can be fulfilled by customizing the control template, I use this. Example, circular progress bar.
Custom control: If control template cannot do it, I use custom control. Provided I need to customize/extend already present control. Example providing Sorting, Filtering based on header row in GridView (GridView is present in metro apps, used just to illustrate the example)
User control: Least preferred one. Only when composition is required, and I am unable to do it using custom control. Like in your example, 2 Combobox, and 1 datagrid. User controls does not provide seamless lookless feature that can be leveraged through custom control or control template.

You already have some great answers that explain the differences but also understand that custom controls and UserControls have different purposes:
A UserControl typically encapusulates some sort of composite behaviour. If you have an application that needs to edit contact details in many places, for example, you could create a custom control that has the labels and text fields for all the data laid out with a submit button that has the relevant code and reuse this control throughout your application.
A custom control is a control that is derived from one of the WPF control classes (E.G. Control, ContentControl etc.) and has to be created in code.
These control usually have a single cohesive purpose (think TextBox, ComboBox, Label) rather than acting together as a whole (although this doesn't have to be the case).
UserControl's are usually easier for people unfamiliar with WPF as they can be visually designed.
My suggestion would be to start off with a UserControl. You can always refactor this into a custom control at a later date as you become more familiar with the way WPF works. Creating your control as a custom control will require knowledge of ControlTemplates and Styles as you will need to provide your own to define a look and feel for your control.
When all is said and done, as long as the control behaves correctly, it doesn't matter which approach you use.
See this post for an example of two approaches to the same problem. The post author wanted a control which can present modal content in front of the primary content. The post author actually answered his own question by implementing it as a UserControl. I have added an answer to the post which creates the control as a custom control but both have the same end effect.

If you have a view-model and you wish to create a view for it use the User-Control.
If you need an autonomous control that has no specific view-model,
you probably need a custom-control.
If you find that the functionality you need as whole, already exist in other controls you need to override an existing control template.
(i.e: for a diamond shaped button - you need to override the button control template.)
Regarding attached-properties and attached-behaviors, those are useful when you have a control which you want to extend with more properties or you want it to behave slightly different than its default behavior.
In the provided case of the composition the OP described, it can be achieved with either user control or custom control. I would prefer a custom control since there is no specific view model provided, the "input" is only a property bound to an item collection.
Oh, and, I am sorry for slightly being late.

The best explanation is in the msdn. CustomControl is more a "virtual" name, there is no class called "CustomControl" in WPF, instead its meant creating a new class building on top of one of WPF control classes, like Control, ItemsControl and even more specific Controls like TextBox or Button.
For your specific case, a UserControl should be enough, creating a CustomControl is something that can easily be avoided. While its not a bad thing, a lot of people, especially beginners in WPF coming from WinForms tend to subclass more then necessary.

If this is somehow your first time building controls, I recommend UserControl as VS lets you design its interface more easily. Custom Controls are more powerful, but you have to CLEARLY separate your control's logic from its interface and this requires a bit more preparation.

You can easily Visually design CustomControl.
Create new UserControl (or Window). Create its xaml structure visually in Designer. Copy-paste body of the resulting xaml inside ControlTemplate of your new CustomControl (Eg. in generic theme file).
If I remember right, you are also able to visually design CustomControl template directly, in Blend.
Of course you can also instance the wip CustomControl in a Window and put the Window's Designer view as new panel above the control's xaml view in VisualStudio.
Some xaml bindings from style template don't show in Designer like this though, until I rebuild.
[ Imho GUI is mainly a visual matter and should not, and doesn't need to, be created in code. ]

Well to create a Custom control you need to implement it as a User control. Your own User control is called a Custom control. It is pretty simple.
UserControl is the base class for containing your custom content :
<UserControl>
Your custom WPF content
</UserControl>
I don't totally agree with the article. However in your case you need a UserControl that you can re-use latter in your UI.

Creating a reusable interface element in WPF

I'm developing a WPF application in C# and was thinking about implementing a custom UI element accross various windows.
I would like to have a minimized tray (only about 4px visible) that expands after clicking on an icon next to the tray. The expanded version would show all controls and would minimize when I click the icon again. I created a quick HTML concept to clarify things.
I know I could put a stackpanel and button in my application and making both of them move up when I click the button, but then I would need to duplicate the code a lot.
Though I'm experienced with C#, I'm fairly new to WPF interface development/templates, but I'm sure there has to be a way so I can use that UI element accross my application without needing to copy/paste a lot of lines of code in my form class file.
I hope someone can help me, or at least point me in the right direction.

There are three ways to customize your elements.
1 If you only need visual modifications you can use styles to change the appearance of the .net default controls. You can even override / extend the default templates.
2 If you want custom logic in a control you can create a custom control. The framework brings a lot of "primitives" to build upon. Examples are ContentControl or HeaderedContentControl. Say you want to build a custom expander control you can inherit your custom control from HeaderedContentControl which provides you with Header and Content properties and you just have to implement the toggling logic yourself.
CustomControls are a good choice if you want to build basic functionality which can be used throughout your application. They can be themed/styled depending on the use case, too (see 1).
3 If you want to compose different controls into one control you can create a UserControl. User controls are composed using XAML. Most top level controls are user controls driven by a view model.
Your case can be build using a Popup and ToggleButton or an Expander.
The decision depends on the desired behavior. If you want the opened panel to move following content down you need a expander. If you want a dropdown like functionality you need popup.
If you use a popup just bind the IsPopupOpen Property to IsChecked of the ToggleButton and set PopupStaysOpen = false to wire the button to your popup.
If you use an expander control you should create a style which can be applied to all equal expanders in your application to minimize the required XAML in each view.

How about using Expander Control?

There's a control called an Expander that is perfect for this. You'll have to style it to look like you want, however it has the functionality you want built-in.

What is the best way to replace controls at runtime?

I'm fairly new to WPF and I have this scenario:
I have an application that contains an area where different sets of controls should be displayed at different time(different application states).
I'm wondering what is the approach in WPF?
In winforms I would make controls visible/invisible at runtime. If there were too many controls I would group them on Panels/UserControls and show/hide those.
My gut tells me there is a better way in WPF.

There are lots of options for doing this in WPF. In addition to hiding and showing individual or groups of controls by setting Visibility, you could use different DataTemplates to contain the set of controls for each state and switch between those. All you need is a ContentControl on which you can set the ContentTemplate. The ContentTemplate value can then be switched to different DataTemplates using a Trigger, a Binding, from code, or by using ContentTemplateSelector to choose a template.

The Visibility property describes your old winforms habits perfectly.
You'll also want to look into Visual States. This will allow you to hide/show multiple controls and even change other properties (i.e. enable state, font color).