如何在c#中使用互操作找到一行的最后字符位置

class Program
{
    static void Main(string[] args)
    {
        Application application = new Application();
        Document document = application.Documents.Open("D:''test.doc");
        if (document.Paragraphs.Count > 0)
        {
            var paragraph = document.Paragraphs.First;
            var lastCharPos = paragraph.Range.Sentences.First.End-1;
            Console.WriteLine(lastCharPos);
        }
        Console.ReadLine();
    }
}