将保存在数据库中的图片信息生成缩略图的问题，请大家指导！

function StorePage(){d=document;t=d.selection?(d.selection.type!='None'?d.selection.createRange().text:''):(d.getSelection?d.getSelection():'');void(keyit=window.open('http://www.365key.com/storeit.aspx?t='+escape(d.title)+'&u='+escape(d.location.href)+'&c='+escape(t),'keyit','scrollbars=no,width=475,height=575,left=75,top=20,status=no,resizable=yes'));keyit.focus();}
我使用的是vs2003 VB.net.

我想把保存在数据库中的图片文件，提取后，生成缩略图显示在网页上，以下是我的代码：

Dim con As New SqlClient.SqlConnection

Dim cmd As New SqlClient.SqlCommand

Dim fjnr() As Byte

con.ConnectionString = dbconstring

cmd.Connection = con

con.Open()

cmd.CommandText = "select fjnr from L_fj where id = " & fjid

fjnr = Convert.FromBase64String(cmd.ExecuteScalar())

Dim sfj As New System.IO.MemoryStream(fjnr)

img = System.Drawing.Image.FromStream(sfj,True)

其中fjid是图片的id号，在执行Dim sfj As New System.IO.MemoryStream(fjnr)时报错，image对象生成失败。

请各位帮忙指教。