How to create a custom control in code-behind in WPF

Question

I have an issue with creating custom controls in wpf. I always intend to create custom controls completely in code-behind in case I need to extend them.

The issue is when I add them in the xaml they are editable. I don't know how to explain but when I click on them, I can write into them. I think it's the way I'm writing my custom controls. Here's a sample code.

public class MyCustomControl : UserControl
{
    public MyCustomControl()
    {
        var button = new Button();

        this.Content = button;    // I always assign the root element to the Content property of the UserControl. I think this is the case
    }
}

As I said when I add MyCustomControl in Xaml part, it works totally fine but when I click on it (again in xaml part) it is editable and I can write into it. What's my problem exactly?

[Edit] I added screen shots

MyCustomControl in normal state MyCustomControl when I click on and write down into it

this is the code-behind

public class MyCustomControl : UserControl
{
    public MyCustomControl()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        this.Content = new Grid() { Background = Brushes.Red };
    }
}

Can you provide a screenshot of your problem?

samar
– samar

2014-05-09 08:39:48 +00:00
Commented May 9, 2014 at 8:39 — samar
– samar, Commented May 9, 2014 at 8:39
Sure. I added screenshots @samar.

user3530012
– user3530012

2014-05-09 08:53:37 +00:00
Commented May 9, 2014 at 8:53 — user3530012
– user3530012, Commented May 9, 2014 at 8:53

Patrick Hofman · Accepted Answer · 2014-05-09 09:52:09Z

1

It seems to me you can just overwrite the Content property as it is not locked in any way.

You could add a delegate on the Coerce of the Content and check using a bool check whether it is your code which is editing the control or some external source.

How to do this?

First read these articles:

Then, use something like this:

Control.ContentProperty.OverrideMetadata(typeof(YourControlName), new PropertyMetadata(null, null, yourCallback));

As another option, you could create the Control as Template (define the Control.Template inside the Control). In this way you don't have to depend on the Content property (It won't affect the template). You can even put in the passed in Content if you want, but you don't need to.

edited May 9, 2014 at 9:52

answered May 9, 2014 at 8:54

Patrick Hofman

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9 Comments

user3530012 Over a year ago

That's a nice idea. I understand what you mean however I do not know how to implement the part "Adding a delegate checking whether it is your code or some external source." could you provide me a sample please?

Patrick Hofman Over a year ago

@user3530012: Found some sources how to do this. See the updated answer.

user3530012 Over a year ago

Well the problem is that Content property is accessible from xaml. I've found a solution to hide a property from xaml part which is to use EditorBrowsable attribute. but it doesn't work on inherited properties. I tried to override the property setter (by using the new keyword) but id didn't help either.

Patrick Hofman Over a year ago

@user3530012: XAML relies on the DependencyProperties, so you are stuck there. I will put another option in.

Patrick Hofman Over a year ago

@user3530012: Did my last update help you? Where are you stuck?

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