从数据库中读取图片问题（参照孟子E章上的方法），有的记录能显示，有的显示不出

[Donald_fu]

Dim myConnection As New SqlConnection("data source=(local);initial catalog=vehiclemis;password=;user id=sa;")
Dim myCommand As New SqlCommand
myCommand.Connection = myConnection

If strMode = "Vehicle" Then
myCommand.CommandText = "Select Vphoto from Vehicle Where VehicleID='" + strImageID + "'"
Else
'myCommand.CommandText = "Select PersonImageType, PersonImage from Person Where PersonID=" + strImageID
End If

Try
myConnection.Open()
Dim myDataReader As SqlDataReader
myDataReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection)
Do While (myDataReader.Read())
'Response.ContentType = "image/pjpeg"
Response.BinaryWrite(CType(myDataReader.Item("Vphoto"), Byte()))
Loop
myConnection.Close()
Catch SQLexc As System.Exception
'Response.Write("Read Failed : " & SQLexc.ToString())
Throw SQLexc
End Try



我有三条记录，一条可以显示出图片，另两条显示不出。跟踪的结果是在Do while语句中就没有进入循环

[cnhgj]

string SQL = "SELECT FileSize, FileData, ContentType FROM tblFile WHERE FileID = "
+ FileID.ToString();

// Create Connection object
OleDbConnection dbConn = new OleDbConnection(GetConnectionString());

// Create Command Object
OleDbCommand dbComm = new OleDbCommand(SQL, dbConn);

// Open Connection
dbConn.Open();

// Execute command and receive DataReader
OleDbDataReader dbRead = dbComm.ExecuteReader();

// Read row
dbRead.Read();

// Clear Response buffer
Response.Clear();

// Set ContentType to the ContentType of our file
Response.ContentType = (string)dbRead["ContentType"];

// Write data out of database into Output Stream
Response.OutputStream.Write((byte[])dbRead["FileData"], 0, (int)dbRead["FileSize"]);

// Close database connection
dbConn.Close();

// End the page
Response.End();