How to pass a input parameter in Script task of SSIS

Today ,I created a script task of SSIS to upload pyisical files into data base.the core codes are as follows:

 1Dim fileStream As FileStream
 2Dim cmd As New OleDbCommand
 3Dim para As OleDbParameter
 4cmd.Connection = conn
 5cmd.CommandType = CommandType.Text
 6   ''Read file Content
 7fileStream = New FileStream(Path.Combine(attFilesFolder, dr("File_Name").ToString()), FileMode.Open)
 8Dim bytes(CInt(fileStream.Length)) As Byte
 9fileStream.Read(bytes, 0, CInt(fileStream.Length))
10cmd.CommandText = "Update dbo.Sys_Pc_Attachment_Temp Set File_Content=@File_Content WHERE Old_Attachment_ID =" + dr("Old_Attachment_ID").ToString()
11para = New OleDbParameter("@File_Content", OleDbType.Binary)
12para.Value = bytes
13para.Direction = ParameterDirection.Input
14cmd.Parameters.Clear()
15cmd.Parameters.Add(para)
16cmd.ExecuteNonQuery()
17

But when i run it ,alwanys get a error:
"Must Declare Variable @File_Content"

 one method to fix it: replcae @File_Content with ? in sal string.