Get object by its Uid in WPF

Question

I have an control in WPF which has an unique Uid. How can I retrive the object by its Uid?

It is a dependency property of any control in wpf or silverlight .. i've managed to solve this, but i was wondering if exists a built-in method. — jose, Dec 11 '09 at 16:33

Matt Hamilton · Accepted Answer · 2009-12-14T04:39:32.493

14

You pretty much have to do it by brute-force. Here's a helper extension method you can use:

private static UIElement FindUid(this DependencyObject parent, string uid)
{
    var count = VisualTreeHelper.GetChildrenCount(parent);
    if (count == 0) return null;

    for (int i = 0; i < count; i++)
    {
        var el = VisualTreeHelper.GetChild(parent, i) as UIElement;
        if (el == null) continue;

        if (el.Uid == uid) return el;

        el = el.FindUid(uid);
        if (el != null) return el;
    }
    return null;
}

Then you can call it like this:

var el = FindUid("someUid");

edited Dec 14 '09 at 04:39

answered Dec 14 '09 at 04:18

Matt Hamilton

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Doesn't `GetChild(parent, N)` have the complexity of O(N) ? The foreach approach seems cleaner (and clearer) to me. – AgentFire Jun 03 '17 at 20:39
As [msdn](https://social.msdn.microsoft.com/Forums/en-US/9b5ff9c2-434a-4324-b896-350e995b645e/automationid-property?forum=vsautotest) states, if AutomationId is not set, WindowsAutomationFramework will default it to *Uid* if set, or to _ControlName_ if set (checked via inspect.exe). So in some cases the tooling for AutomationIds suffices. – RuNe Feb 11 '19 at 20:16

score 5 · Answer 2 · answered Dec 10 '12 at 11:07

public static UIElement GetByUid(DependencyObject rootElement, string uid)
{
    foreach (UIElement element in LogicalTreeHelper.GetChildren(rootElement).OfType<UIElement>())
    {
        if (element.Uid == uid)
            return element;
        UIElement resultChildren = GetByUid(element, uid);
        if (resultChildren != null)
            return resultChildren;
    }
    return null;
}

score 2 · Answer 3 · edited Feb 20 '14 at 17:52

2

This is better.

public static UIElement FindUid(this DependencyObject parent, string uid) {
    int count = VisualTreeHelper.GetChildrenCount(parent);

    for (int i = 0; i < count; i++) {
        UIElement el = VisualTreeHelper.GetChild(parent, i) as UIElement;
        if (el != null) {
            if (el.Uid == uid) { return el; }
            el = el.FindUid(uid);
        }
    }
        return null;
}

edited Feb 20 '14 at 17:52

SyntaxRules

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answered Jul 24 '12 at 18:59

Mike

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It cannot be better if your code does not work. Your recursion is broken. The result of `el.FindUid(uid)`, if not null, must be returned. – jchristin Sep 29 '15 at 12:50

score 1 · Answer 4 · answered Feb 16 '17 at 15:44

An issue I had with the top answer is that it won't look inside content controls (such as user controls) for elements within their content. In order to search inside these I extended the function to look at the Content property of compatible controls.

public static UIElement FindUid(this DependencyObject parent, string uid)
{
    var count = VisualTreeHelper.GetChildrenCount(parent);

    for (int i = 0; i < count; i++)
    {
        var el = VisualTreeHelper.GetChild(parent, i) as UIElement;
        if (el == null) continue;

        if (el.Uid == uid) return el;

        el = el.FindUid(uid);
        if (el != null) return el;
    }

    if (parent is ContentControl)
    {
        UIElement content = (parent as ContentControl).Content as UIElement;
        if (content != null)
        {
            if (content.Uid == uid) return content;

            var el = content.FindUid(uid);
            if (el != null) return el;
        }
    }
    return null;
}

Get object by its Uid in WPF

4 Answers4

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