Create an instance of a C# class from inside XAML

Question

I have a working application that has been written in C#, and I now want to extend that application to allow the user to switch between viewing the application, and viewing a built in web browser (inside the same application window).

I also have a separate working web browser, that has also been written in C#.

I have just added the functionality to the original application to include 'tabbed' displays, where the original application will be displayed on the first tab, and a built in web browser on the second tab.

The 'tabbed' displays for the application have been created using XAML markup in Visual Studio. I now want to add an instance of the Web browser that has also been written in C# to the second tab that I have created in the XAML markup.

It would be something like:

<TabControl>
        <TabItem Header="Browser">
            <StackPanel>
                <!-- Call/ instantiate the browser here -->
            </StackPanel>
        </TabItem>
</TabControl>

But I have no idea how I call/ create an instance of the browser from within the XAML markup...

The browser has been created using C#:

namespace Agent
{
    public partial class Browser : Form
    {
        public Browser()
        {
            ...
        }
    }
}

Can anyone explain to me how a create an instance of Browser inside the ` of the XAML markup?

Edit

Ok, so I have edited my XAML markup as recommended in the answer that's been suggested- I now have:

<Window ...
  xmlns:Agent="clr-namespace:Agent"
  ...>
    <Grid>
        ...
        <TabControl>
            <TabItem Header="R">
                <StackPanel>
                    ...
                </StackPanel>
            </TabItem>
            <TabItem Header="Browser">
                <Agent:Browser x:Name="Browser" />
            </TabItem>
        </TabControl>
    </Grid>
</Window>

I have also updated my Browser.cs class, so that it is now extending UserControl, rather than Form:

public partial class Browser : UserControl{

However, I am getting a compile error on the line:

<Agent:Browser x:Name="Browser" />

which says:

The name "Browser" does not exist in the namespace "clr-namespace:Agent".

But clearly Browser does exist in Agent, as shown by the code I've included here... In fact, when typing the line <Agent:Browser x:Name="Browser />, when I typed the :, Browser was one of the options that came up in the autocomplete menu...

What am I doing wrong here? Why doesn't the compiler think that Browser exists inside Agent?

Answer 1

The key to instantiating any object in XAML is to make sure the namespace is declared. You can provide any XML prefix and assign it to your CLR namespace (ref) and it will act like a using statement. For example:

<TabControl xmlns:agent="clr-namespace:Agent">
    <TabItem Header="Browser">
        <StackPanel>
            <agent:Browser/>
        </StackPanel>
    </TabItem>
</TabControl>

NOTE: your object has to extend UIElement (or one of its children) for it to work in a XAML tree. If your control is a WinForms control you either need to find the equivalent XAML control or wrap it in a WindowsFormsHost (ref).

---

WPF vs. WinForms

The purpose of this section is to help recognize which platform code is by namespace, as well as some of the trade-offs. I've used both and can say from experience that they each have good points and... not so good points.

• WinForms classes live in the System.Windows.Forms namespace, and are available by referencing the System.Windows.Forms.dll assembly.
• WPF classes live in the System.Windows and System.Windows.Controls namespaces, and are available by referencing a set of DLLs
• WinForms rendering is immediate. That means you are working against bitmaps and you are responsible for clearing and redrawing stuff yourself (usually you can just call Invalidate()). If you do heavy image bit manipulation, WinForms is easier to work with.
• WPF rendering is declarative. That means more work is offloaded to your GPU and you just tell it how to draw stuff. You can also use GPU render shaders for special effects. WPF has a nicer look out of the box, but it has a reputation for making easy things difficult but impossible things possible.
• WinForms is easier to learn, but has a dated look out of the box.
• WPF is built around data binding, enabling the UI to update in response to property values automatically. It's also able to be completely restyled, although that is quite an undertaking.

If you are just getting started, I'd go ahead and bite the bullet to start the heavier learning curve for WPF. It will provide a basic understanding that transfers to other platforms like Windows Store apps, etc.