Menu.ItemTemplate is showing className instead of assigned variable

Question

I created a menu with a dynamic MenuItem list by doing the following:

<Menu VerticalAlignment="Top" Items="{Binding FileList}">
    <Menu.ItemTemplate>
        <DataTemplate>
            <MenuItem Command="{Binding FileClick}" CommandParameter="{Binding FilePath}" Header="{Binding FileName}"/>
        </DataTemplate>
    </Menu.ItemTemplate>
</Menu>

But instead of showing the FileName in the header, it shows the class enter image description here

This is the var that contains the list of menu items:

[ObservableProperty]
public ObservableCollection<EditorMenuItem> fileList = new ObservableCollection<EditorMenuItem>();

And this is how I add an item into the list:

fileList.Add(new EditorMenuItem(
    "test1",
    "C:/test1.txt",
    ReactiveCommand.Create<string>((string fileName) =>
    {
        HandleFileClick(fileName);
    })
));

The EditorMenuItem class looks like this:

public class EditorMenuItem
{
    public string FileName;
    public string FilePath;
    public ICommand FileClick;

    public EditorMenuItem(string FileName, string FilePath, ICommand FileClick)
    {
        this.FileName = FileName;
        this.FilePath = FilePath;
        this.FileClick = FileClick;
    }
}

Does anyone know what the problem is and why I get the className instead of the actual FileName?