XML 序列化程式產生器工具
.NET程式在做XML序列化時，在效能上表現並不佳，因此提供了XML 序列化程式產生器工具來改善這個問題。使用XML 序列化程式產生器工具，可為指定組件中的型別建立 XML 序列化 (Serialization) 組件，以改善 XmlSerializer 在序列化或還原序列化指定型別物件時的啟動效能。 如果未使用 XML 序列化程式產生器，為指定組件中的型別建立XML 序列化組件。則每當應用程式執行時，XmlSerializer 便會為每個型別產生序列化程式碼和序列化組件，造成XML序列化緩慢。
何謂XML序列化組件呢?換句話說就是使用XML 序列化程式產生器所產生出來的檔案，也就是檔案命名後半部為XmlSerializers.dll的檔案，像是Data.XmlSerializers.dll。
這邊我們可以寫個簡單的程式來觀察這個現象，程式碼如下： Imports System.Xml.Serialization Imports System.IO
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim count As Integer = 1 Dim perosn As New Person Dim xs As New XmlSerializer(GetType(Person)) Dim sw As Stopwatch = Stopwatch.StartNew Using ms As New MemoryStream For i As Integer = 0 To count - 1 ms.Seek(0, SeekOrigin.Begin) xs.Serialize(ms, perosn) Next End Using MsgBox(“ElapsedMilliseconds: " & sw.ElapsedMilliseconds) End Sub End Class
Public Class Person Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _ End Set End Property
Private _year As Integer Public Property Year() As Integer Get Return _year End Get Set(ByVal value As Integer) _year = value End Set End Property End Class
運行後用ProcessMonitor去觀察，可發現當第一次執行到建立XmlSerializer物件的程式碼時，背後就在偷偷的找尋並試圖建立XML序列化組件。
使用XML 序列化程式產生器工具
要熟悉如何使用XML 序列化程式產生器工具來加速XML序列化的動作，先來看一下Sgen.Exe的用法。
Usage: sgen.exe [[/assembly:] | []]
[/type:] [/reference:] [/compiler:] [/debug] [/keep] [/nologo]
[/silent] [/verbose]
Developer options:
/assembly: Assembly location or display name. Short form is ‘/a:’.
/type: Generate code for serialization/deserialization of a single
type from the input assembly. Short form is ‘/t:’.
/reference: Reference metadata from the specified assembly files.
Short form is ‘/r:’.
/compiler: Visual C# compiler options to use while compiling generated
code. Short form is ‘/c’.
For complete list of available options see c# compiler help.
/proxytypes Generate serialization code only for proxy classes and web
method parameters. Short form is ‘/p’.
/debug Generate image which can be used under a debugger.
Short form is ‘/d’.
/keep Keep source code and compiler temp files. Short form is ‘/k’.
/force Forces overwrite of a previously generated assembly.
Short form is ‘/f’.
/out: Output directory name (default: target assembly location).
Short form is ‘/o:’.
/parsableerrors
Print errors in a format similar to those reported by
compilers.
Miscellaneous options:
/? or /help Show this message
/nologo Prevents displaying of logo. Short form is ‘/n’.
/silent Prevents displaying of success messages. Short form is ‘/s’.
/verbose Displays verbose output for debugging. Short form is ‘/v’.
List types from the target assembly that cannot be serialized
with XmlSerializer.
最簡單的用法就是直接在命令後面接上組件名稱，像是：
Sgen XXX.dll
若產生的檔案可能已經存在，可加上/f參數強迫覆蓋。而若無法正確的產生XML序列化組件，可加上/v參數顯示造成無法產生的錯誤訊息。
使用上可在[專案]→[屬性]→[編譯]→[建置事件]內的建置後事件加上如下命令(命令路徑請依電腦實際狀況去做調整)：
“%ProgramFiles%\Microsoft SDKs\Windows 7.0Ain\sgen.exe” /a:"$(TargetPath)” /force
如此建置後將在輸出目錄自動產生對應的XML序列化組件，將產生的XML序列化組件與自己撰寫的組件放在一起，序列化的速度就會提升了。
若仍嫌速度緩慢，也可以把產生的序列化組件加入參考，匯入Microsoft.Xml.Serialization.GeneratedAssembly命名空間，改用序列化組件內的Serializer取代XmlSerializer，像是：
Imports System.Xml.Serialization Imports System.IO Imports Microsoft.Xml.Serialization.GeneratedAssembly
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim count As Integer = 1000 Dim perosn As New Person Dim xs As New PersonSerializer Dim sw As Stopwatch = Stopwatch.StartNew Using ms As New MemoryStream For i As Integer = 0 To count - 1 ms.Seek(0, SeekOrigin.Begin) xs.Serialize(ms, perosn) Next End Using MsgBox(“ElapsedMilliseconds: " & sw.ElapsedMilliseconds) End Sub End Class
效能測試
這邊針對校能的改進作了一些測試，測試的CODE沿用上面的範例，實驗數據與結果如下：
次數
無XML序列化組件
有XML序列化組件
使用XML序列化組件的Serialzer
1000
125
107
84
10000
946
884
597
100000
7382
5909
5924
1000000
62892
59159
44779
Link
XML 序列化程式產生器工具 (Sgen.exe)