【dinghao】asp.net控制元件開發（一）簡單屬性、檢視狀態、控制元件狀態
瞭解控制元件的生命週期：
其中Init是由內而外，即先子控制元件後父控制元件，Load等相反。
在Init之前控制元件樹根據宣告語法已經生成
控制元件狀態和檢視狀態：
控制元件狀態是專門為維護控制元件的核心行為功能而設計的，而 ViewState 只包含維護控制元件內容 (UI) 的狀態。應該按照這個規則設計控制元件狀態。
先看一個例子：改自asp伺服器控制元件和元件開發一書
PageTracker，用來跟蹤頁面會話狀態和程式狀態收到的點選數目，並計算頁面往返時間
跟蹤方式：
<!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
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-->
public enum PageTrackingMode
{
ByApplication,
BySession,
ByTripTime
}控制元件程式碼：
<!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
--> [
DefaultProperty("TrackingMode")
]
public class PageTracker : WebControl {
private TimeSpan _tripTime;
[
Category("Appearance"),
DefaultValue("{0}"),
Description("The formatting string used to display the value being tracked.")
]
public virtual string FormatString {
get {
string s = (string)ViewState["FormatString"];
return ((s == null) ? "{0}" : s);
}
set {
ViewState["FormatString"] = value;
}
}
[
Browsable(false),
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)
]
public int Hits {
get {
PageTrackingMode mode = TrackingMode;
object o = null;
if (mode == PageTrackingMode.ByApplication) {
o = Page.Application[HitsKey];
}
else if (mode == PageTrackingMode.BySession) {
o = Page.Session[HitsKey];
}
else {
throw new NotSupportedException("Hits is only supported when TrackingMode is PageTrackingMode.ByApplication or PageTrackingMode.BySession");
}
return ((o == null) ? 0 : (int)o);
}
}
[
Category("Behavior"),
DefaultValue(PageTrackingMode.ByApplication),
Description("The type of tracking to perform.")
]
public virtual PageTrackingMode TrackingMode {
get {
object mode = ViewState["TrackingMode"];
return ((mode == null) ? PageTrackingMode.ByApplication : (PageTrackingMode)mode);
}
set {
if (value < PageTrackingMode.ByApplication || value > PageTrackingMode.ByTripTime) {
throw new ArgumentOutOfRangeException("value");
}
ViewState["TrackingMode"] = value;
// Perform cleanup of the old storage.
// We have to check that the Page is not null
// because the control could be initialized
// before it is added to the control tree.
// 因為 Application and Session
// 在設計時不可用，所以會出現異常
switch (TrackingMode) {
case PageTrackingMode.ByApplication:
if (Page != null && Page.Application != null) {
Page.Application.Remove(HitsKey);
}
break;
case PageTrackingMode.BySession:
if (Page != null && Page.Session != null) {
Page.Session.Remove(HitsKey);
}
break;
case PageTrackingMode.ByTripTime:
ViewState.Remove("TimeStamp");
break;
}
}
}
[
Browsable(false),
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)
]
public TimeSpan TripTime {
get {
if (TrackingMode != PageTrackingMode.ByTripTime) {
throw new NotSupportedException("TripTime is only supported when TrackingMode is PageTrackingMode.ByTripTime");
}
return _tripTime;
}
}
protected override HtmlTextWriterTag TagKey {
get {
return HtmlTextWriterTag.Div;
}
}
private string HitsKey {
get {
// Create a unique HitsKey for the page for keying
// in hits per page in the Application and Session objects.
return Page.GetType().FullName;
}
}
protected override void OnLoad(EventArgs e) {
base.OnLoad(e);
switch (TrackingMode){
case PageTrackingMode.ByApplication:
// Update the page hits in the Application
// object. This operation needs a lock because
// multiple users could access a page at the same
// time.
其中Init是由內而外，即先子控制元件後父控制元件，Load等相反。
在Init之前控制元件樹根據宣告語法已經生成
控制元件狀態和檢視狀態：
控制元件狀態是專門為維護控制元件的核心行為功能而設計的，而 ViewState 只包含維護控制元件內容 (UI) 的狀態。應該按照這個規則設計控制元件狀態。
先看一個例子：改自asp伺服器控制元件和元件開發一書
PageTracker，用來跟蹤頁面會話狀態和程式狀態收到的點選數目，並計算頁面往返時間
跟蹤方式：
<!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
-->
public enum PageTrackingMode { ByApplication, BySession, ByTripTime }<!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
http://www.CodeHighlighter.com/
-->
[ DefaultProperty("TrackingMode") ] public class PageTracker : WebControl { private TimeSpan _tripTime; [ Category("Appearance"), DefaultValue("{0}"), Description("The formatting string used to display the value being tracked.") ] public virtual string FormatString { get { string s = (string)ViewState["FormatString"]; return ((s == null) ? "{0}" : s); } set { ViewState["FormatString"] = value; } } [ Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden) ] public int Hits { get { PageTrackingMode mode = TrackingMode; object o = null; if (mode == PageTrackingMode.ByApplication) { o = Page.Application[HitsKey]; } else if (mode == PageTrackingMode.BySession) { o = Page.Session[HitsKey]; } else { throw new NotSupportedException("Hits is only supported when TrackingMode is PageTrackingMode.ByApplication or PageTrackingMode.BySession"); } return ((o == null) ? 0 : (int)o); } } [ Category("Behavior"), DefaultValue(PageTrackingMode.ByApplication), Description("The type of tracking to perform.") ] public virtual PageTrackingMode TrackingMode { get { object mode = ViewState["TrackingMode"]; return ((mode == null) ? PageTrackingMode.ByApplication : (PageTrackingMode)mode); } set { if (value < PageTrackingMode.ByApplication || value > PageTrackingMode.ByTripTime) { throw new ArgumentOutOfRangeException("value"); } ViewState["TrackingMode"] = value; // Perform cleanup of the old storage. // We have to check that the Page is not null // because the control could be initialized // before it is added to the control tree. // 因為 Application and Session // 在設計時不可用，所以會出現異常 switch (TrackingMode) { case PageTrackingMode.ByApplication: if (Page != null && Page.Application != null) { Page.Application.Remove(HitsKey); } break; case PageTrackingMode.BySession: if (Page != null && Page.Session != null) { Page.Session.Remove(HitsKey); } break; case PageTrackingMode.ByTripTime: ViewState.Remove("TimeStamp"); break; } } } [ Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden) ] public TimeSpan TripTime { get { if (TrackingMode != PageTrackingMode.ByTripTime) { throw new NotSupportedException("TripTime is only supported when TrackingMode is PageTrackingMode.ByTripTime"); } return _tripTime; } } protected override HtmlTextWriterTag TagKey { get { return HtmlTextWriterTag.Div; } } private string HitsKey { get { // Create a unique HitsKey for the page for keying // in hits per page in the Application and Session objects. return Page.GetType().FullName; } } protected override void OnLoad(EventArgs e) { base.OnLoad(e); switch (TrackingMode){ case PageTrackingMode.ByApplication: // Update the page hits in the Application // object. This operation needs a lock because // multiple users could access a page at the same // time.來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/12639172/viewspace-332340/，如需轉載，請註明出處，否則將追究法律責任。
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