Is there any unique identifier for wpf UIElement?

One way you can do this is with a custom attribute. Like so...

The UIElement you want to log (UserControl for example):

[UserInterfaceID(ID = "{F436E9B3-C2F6-4CF8-8C75-0A2A756F1C74}")]
public partial class MyUserControl : UserControl
{
    InitializeComponent();
    // or whatever...
}

Then you need the custom attribute class

[System.AttributeUsage(AttributeTargets.Class)]
public class UserInterfaceIDAttribute : Attribute
{
    public Guid ID { get; set; }
}

Now in your code, you can do something like this:

MyUserControl control = new MyUserControl();
foreach(object att in control.GetCustomAttributes(typeof(UserInterfaceAttribute),false))
{
    UserInterfaceAttribute uiAtt = (UserInterfaceAttribute)att;
    Guid theID = uiAtt.ID;
}

Because you are tagging the control with an attribute in the code, the unique identifier never changes no matter how many times you kill / launch the application.

Of course this is a basic example that shows how to access the ID but you will probably want to use some type of Aspect Oriented Programming. I do exactly this kind of thing using Castle Windsor Interceptors, but that is out of the scope of this post.

Ideally, you will be accessing this ID when there is some kind of event that gets fired. Using interceptors allows you go capture method calls before they are invoked wherein you can look up the ID as shown above and log the action. Alternatively, you can just use

this.GetCustomAttributes(...)

in some method when an event is fired on the control and embed your Logging code there. This pattern is not the best because you're sprinkling cross-cutting concerns all over making some type of Aspect Oriented Programming approach better...but again I digress and it is out of the scope of this post...but you get the idea.

Hope this helps.

Why don't you use the Hash Code.

You can compare the values to make sure they are the same object, and its easy to get them with .GetHashCode()

---

Edit

Obviously this is different every time you run the program, so actually this is prolly a bad idea, unless you want to update the log each time the process is logged. Still possible though

I mean you could store a hash value for each object at the time the log is created, but i don't know if I like that

Seems I found answer to my question, the answer is No, now way to do that, As noted in MSDN here (http://msdn.microsoft.com/en-us/magazine/dd483216.aspx)

Notice that the top-level Window control definition does not contain a Name attribute. This is significant because, as we'll see shortly, when you write test automation, an easy way to get a reference to a control using the MUIA library is to access the AutomationId property, which is generated by the compiler from the control's Name attribute. Controls without a XAML Name attribute will not receive an AutomationId property. This idea is a specific, low-level example of the importance of considering application design issues for things such as security, extensibility, and test automation.