FileStream fs = new FileStream(path, FileMode.Open); 
  byte[] data = new byte[fs.Length]; 
  fs.Read(data, 0, data.Length); 
  fs.Close();
  MemoryStream ms = new MemoryStream(data);

------解决方案--------------------

  ///定义并实例化一个内存流，以存放图片的字节数组。 
 MemoryStream m = new MemoryStream(); 
 ///获得当前路径 
 string strAppPath = AppDomain.CurrentDomain.BaseDirectory; //获得可执行文件的路径。 
 ///获得图片路径  
 string strPath = strAppPath + "img\\default.jpg";  
 ///图片读入FileStream  
 FileStream f = new FileStream(strPath, FileMode.open);  
 ///把FileStream写入MemoryStream  
 m.SetLength(f.Length);  
 f.Read(m.GetBuffer(), 0, (int)f.Length);  
 m.Flush();  
 f.Close(); 


------解决方案--------------------
C# code
            FileStream fs = new FileStream(fileName, FileMode.Open);
            byte[] MyData = new byte[fs.Length];
            fs.Read(MyData, 0, (int)fs.Length);
            fs.Close();
            MemoryStream ms = new MemoryStream(MyData);

------解决方案--------------------
C# code
MemoryStream ms = new MemoryStream(File.ReadAllBytes("c:\\1.jpg"));