how to use System.Windows.Forms.FolderBrowserDialog in .net6 wpf

In .NET 6 and later versions, the `System.Windows.Forms` namespace is not included in the default installation of WPF applications. However, you can still use the `FolderBrowserDialog` class in your WPF application by adding a reference to the `System.Windows.Forms` NuGet package and using the `System.Windows.Forms.Integration` namespace.

Here are the steps to use `FolderBrowserDialog` in .NET 6 WPF:

1. Add a reference to the `System.Windows.Forms` NuGet package in your WPF project.

2. Add the following using statements to the top of your code file:

using System.Windows.Forms;
using System.Windows.Forms.Integration;

3. In your code, create a `FolderBrowserDialog` object and use the `ShowDialog` method to display the dialog box:

FolderBrowserDialog dialog = new FolderBrowserDialog();

if (dialog.ShowDialog() == DialogResult.OK)
{
    // do something with the selected folder
}

4. If you want to use the `FolderBrowserDialog` in a WPF window or page, you can use the `WindowsFormsHost` control to host the dialog box:

<Window xmlns:winforms="clr-namespace:System.Windows.Forms.Integration;assembly=WindowsFormsIntegration"
        xmlns:forms="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
        ...>
    <Grid>
        <winforms:WindowsFormsHost>
            <forms:FolderBrowserDialog x:Name="folderDialog" />
        </winforms:WindowsFormsHost>
    </Grid>
</Window>

Then, you can use the `ShowDialog` method to display the dialog box:

if (folderDialog.ShowDialog() == DialogResult.OK)
{
    // do something with the selected folder
}

Note that you will also need to add a reference to the `WindowsFormsIntegration` assembly in your WPF project.