中控指纹仪AddImageFile

用中控指纹仪的axZKFPEngX.AddImageFile总是返回false，不知道该怎么用这个方法？
           if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                string sFileName = openFileDialog.FileName;
                Bitmap btm = new Bitmap(sFileName);
                Image img = Image.FromFile(sFileName);
                axZKFPEngX.EnrollCount = 1;
                btnEnroll.PerformClick();
                if (axZKFPEngX.AddImageFile(sFileName, 96*96))
                {
                    toolStripStatusLabel.Text = "导入成功。";
                }
                else
                {
                    toolStripStatusLabel.Text = "导入失败。";
                }
            } 中控指纹仪  AddImageFile bitmap

补充：.NET技术 ,  C#