WPF bind item command to parent

gistfile1.cs

//WPF part
<ItemsControl ItemsSource="{Binding companyList}">
  <ItemsControl.ItemTemplate>
    <DataTemplate>
      <RadioButton Command="{Binding Path= DataContext.ChooseCompanyCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}}" CommandParameter="{Binding CompanyID}" GroupName="Company" Content="{Binding CompanyName}"/>
    </DataTemplate>
  </ItemsControl.ItemTemplate>
</ItemsControl>

//ViewModel
public CompanyInfoList companyList { get; private set; }
public DelegateCommand<string> ChooseCompanyCommand { get; set; }

  //Constructor
public ReportDokumentViewModel()
{
  //...
  ChooseCompanyCommand = new DelegateCommand<string>(SetCompany, o => true);
}

public void SetCompany(string parameter)
{
    //... LOGIC
}