平台建设网站,邢台做网站改版,外贸自建站多少钱,长春网站建设团队接着上文Asp.net TextBox的TextChanged事件你真的清楚吗#xff1f; 这里我们来说说状态数据时如何加载的。虽然在Control中有调用状态转存的方法#xff0c;但是这里有一个判断条件 if (_controlState ControlState.ViewStateLoaded) 一般的get请求这里的条件是不满足…接着上文Asp.net TextBox的TextChanged事件你真的清楚吗 这里我们来说说状态数据时如何加载的。虽然在Control中有调用状态转存的方法但是这里有一个判断条件 if (_controlState ControlState.ViewStateLoaded) 一般的get请求这里的条件是不满足的。 internal enum ControlState { Constructed, FrameworkInitialized, ChildrenInitialized, Initialized, ViewStateLoaded, Loaded, PreRendered } 我们知道在page的ProcessRequest中this.ControlState ControlState.FrameworkInitialized; ProcessRequestMain方法中在Init后有调用this.InitRecursive(null);在这个方法里面有这么一句_controlState ControlState.Initialized;在LoadAllState()方法中有这么一句 base.LoadViewStateRecursive(second.Second);而LoadViewStateRecursive中又有_controlState ControlState.ViewStateLoaded这句带代码所以我们在Page_load中动态条件控件时 if (_controlState ControlState.ViewStateLoaded)条件成立如图 所以在运行this.form1.Controls.Add(txt);这句以前txt的值为demo1 如图 但是运行以后之就发生变化了 当然这里的txt.Text值也是我上次post过来的旧值新值是在控件的LoadPostData方法中重新绑定。在默认的LoadViewStateRecursive方法中有一个很重要的判断 internal void LoadViewStateRecursive(object savedState) { // nothing to do if we have no state if (savedState null || flags[disableViewState]) return; 。。。。。。。 _controlState ControlState.ViewStateLoaded } 大家看到我上面是一个CustTextBoxt : TextBox控件如果我们直接添加TextBox控件的话那么着这里的txt.Text一直都是demo1可见控件动态添加的时候是否加载状态数 据与状态数据的保存有关。而状态数据的保存主要就是SaveViewState完成的这里我第一次post的时候SaveViewState返回数据 所以第二次能取到上次post过来的数据。 其中与SaveViewState有关的方法主要有 public class TextBox : WebControl, IPostBackDataHandler, IEditableTextControl {protected override object SaveViewState() {if (SaveTextViewState false) {ViewState.SetItemDirty(Text, false);}return base.SaveViewState();}private bool SaveTextViewState {get {//// Must be saved when// 1. There is a registered event handler for SelectedIndexChanged// 2. Control is not enabled or visible, because the browsers post data will not include this control// 3. The instance is a derived instance, which might be overriding the OnTextChanged methodif (TextMode TextBoxMode.Password) {return false;}if ((Events[EventTextChanged] ! null) ||(IsEnabled false) ||(Visible false) ||(ReadOnly) ||(this.GetType() ! typeof(TextBox))) {return true;}return false;}}}public class WebControl : Control, IAttributeAccessor {protected override object SaveViewState() {Pair myState null;// Save values cached out of view stateif (_webControlFlags[disabledDirty]) {ViewState[Enabled] !flags[isWebControlDisabled];}if (ControlStyleCreated) {// the style shares the StateBag of its owner WebControl// call SaveViewState to let style participate in state managementControlStyle.SaveViewState();}object baseState base.SaveViewState();object aState null;if (attrState ! null) {aState attrState.SaveViewState();}if (baseState ! null || aState ! null) {myState new Pair(baseState, aState);}return myState;}
}
public class Control : IComponent, IParserAccessor, IUrlResolutionService, IDataBindingsAccessor, IControlBuilderAccessor, IControlDesignerAccessor, IExpressionsAccessor {protected virtual object SaveViewState() {// Save values cached out of view stateif (flags[visibleDirty]) {ViewState[Visible] !flags[invisible];}if (flags[validateRequestModeDirty]) {ViewState[ValidateRequestMode] (int)ValidateRequestMode;}if (_viewState ! null)return _viewState.SaveViewState();return null;}
}
public sealed class StateBag : IStateManager, IDictionary {internal object SaveViewState() {ArrayList data null;if (bag.Count ! 0) {IDictionaryEnumerator e bag.GetEnumerator();while (e.MoveNext()) {StateItem item (StateItem)(e.Value);if (item.IsDirty) {if (data null) {data new ArrayList();}
#if OBJECTSTATEFORMATTERdata.Add(new IndexedString((string)e.Key));
#elsedata.Add(e.Key);
#endifdata.Add(item.Value);}}}return data;}} 到这里我们知道保存状态信息主要是在StateBag 的SaveViewState方法中这里有一个检查 if (item.IsDirty) 在TextBox的SaveViewState方法中有一个判断 if (SaveTextViewState false) { ViewState.SetItemDirty(Text, false); } 与它的SaveTextViewState 属性有关。 那么我们可以总结一下动态创建的控件默认是在被添加的时候加载器状态数据如果是静态添加的数据那就是LoadAllState来处理状态数据的加载。状态数据的加载与控件的SaveViewState密切相关如果该方法的返回值为null既没有状态信息那也不需要加载什么状态信息了。转载于:https://www.cnblogs.com/majiang/archive/2012/12/11/2813072.html
