一个简单的使用open xml向SharePoint文档库中的文档添加文本的方法示例：

            public void AddTextToFile(SPFile file,string myText)
            {
                byte[] byteArray = file.OpenBinary();
                using (MemoryStream memStr = new MemoryStream())
                {
                    memStr.Write(byteArray,byteArray.Length);
                    using (WordprocessingDocument wordDoc = WordprocessingDocument.Open(memStr,true))
                    {
                        Document document = wordDoc.MainDocumentPart.Document;
                        Paragraph firstParagraph = document.Body.Elements<Paragraph>().FirstOrDefault();
                        if (firstParagraph != null)
                        {
                            Paragraph testParagraph = new Paragraph(
                                new Run(
                                    new Text(myText)));
                            firstParagraph.Parent.InsertBefore(testParagraph,firstParagraph);
                        }
                    }

                    string linkFileName = file.Item["LinkFilename"] as string;
                    file.ParentFolder.Files.Add(linkFileName,memStr,true);
                }
             }