Root element is missing

最新写一段代码,实现功能
1. 把上传文档转换成byte[]传会给调用方法;
2. 同时返回out xmldocument 对象;
如下:

protected Byte[] GetFile(FileUpload FileUploadFile,out XmlDocument xmlDoc)
        {
            string strFilePathName = FileUploadFile.PostedFile.FileName.Trim();
            string strFileName = Path.GetFileName(strFilePathName);
            int FileLength = FileUploadFile.PostedFile.ContentLength;
            Byte[] FileByteArray = new Byte[FileLength];
            Stream StreamObject = FileUploadFile.PostedFile.InputStream;
            StreamObject.Read(FileByteArray, 0, FileLength);

            //Out a xml document object
            XmlDocument xmlDoctmp = new XmlDocument();

            xmlDoctmp.Load(StreamObject);

            xmlDoc = xmlDoctmp;

            xmlDoctmp = null;

            return FileByteArray;
        }
编译抛出Exception:
....Root element is missing.....

原因&解决方案:
StreamObject.Read类似游标功能,在StreamObject.Read(FileByteArray, 0, FileLength);该游标已经从文件开始读到文件结束,
所以,必须重新设置游标位置,代码更改如下:

protected Byte[] GetFile(FileUpload FileUploadFile,out XmlDocument xmlDoc)
        {
            string strFilePathName = FileUploadFile.PostedFile.FileName.Trim();
            string strFileName = Path.GetFileName(strFilePathName);
            int FileLength = FileUploadFile.PostedFile.ContentLength;
            Byte[] FileByteArray = new Byte[FileLength];
            Stream StreamObject = FileUploadFile.PostedFile.InputStream;
            StreamObject.Read(FileByteArray, 0, FileLength);

            //Out a xml document object
            XmlDocument xmlDoctmp = new XmlDocument();

            StreamObject.Position = 0;

            xmlDoctmp.Load(StreamObject);

            xmlDoc = xmlDoctmp;

            xmlDoctmp = null;

            return FileByteArray;

        }

编译通过