[DllImport("comctl32.dll", PreserveSig = false)]
private static extern void TaskDialogIndirect([In] ref TaskDialogConfig pTaskConfig, out int pnButton,
    out int pnRadioButton, [MarshalAs(UnmanagedType.Bool)] out bool pfVerificationFlagChecked);

// ...

var config = new TaskDialogConfig
{
    pszWindowTitle = "Task dialog title",
    pszMainInstruction = "Task dialog main instruction",
    dwCommonButtons = TaskDialogCommonButtonFlags.OkButton | TaskDialogCommonButtonFlags.CancelButton,
    // ...
};

using (new ComCtlv6ActivationContext(enable: true))
{
    TaskDialogIndirect(ref config, out _, out _, out _);
}