PageRequestManager.OnInit

internal sealed class PageRequestManager
{// ...internal void OnInit(){if (_owner.EnablePartialRendering && !_owner._supportsPartialRenderingSetByUser){IHttpBrowserCapabilities browser = _owner.IPage.Request.Browser;bool supportsPartialRendering =(browser.W3CDomVersion >= MinimumW3CDomVersion) &&(browser.EcmaScriptVersion >= MinimumEcmaScriptVersion) &&browser.SupportsCallback;if (supportsPartialRendering){supportsPartialRendering = !EnableLegacyRendering;}_owner.SupportsPartialRendering = supportsPartialRendering;}}// ...
}

代码实现

internal static class AjaxFileUploadUtility
{internal static bool IsInIFrameAsyncPostBack(NameValueCollection requestBody){ string[] values = requestBody.GetValues("__AjaxFileUploading__");if (values == null) return false;foreach (string value in values){if (value == "__IsInAjaxFileUploading__"){return true;}}return false;}// ...
}
[PersistChildren(false)]
[ParseChildren(true)]
[NonVisualControl]
public class AjaxFileUploadHelper : Control
{// ScriptManager members;private static FieldInfo isInAsyncPostBackFieldInfo;private static PropertyInfo pageRequestManagerPropertyInfo;// PageRequestManager members;private static MethodInfo onPageErrorMethodInfo;private static MethodInfo renderPageCallbackMethodInfo;static AjaxFileUploadHelper(){Type scriptManagerType = typeof(ScriptManager);isInAsyncPostBackFieldInfo = scriptManagerType.GetField("_isInAsyncPostBack",BindingFlags.Instance | BindingFlags.NonPublic);pageRequestManagerPropertyInfo = scriptManagerType.GetProperty("PageRequestManager",BindingFlags.Instance | BindingFlags.NonPublic);Assembly assembly = scriptManagerType.Assembly;Type pageRequestManagerType = assembly.GetType("System.Web.UI.PageRequestManager");onPageErrorMethodInfo = pageRequestManagerType.GetMethod("OnPageError", BindingFlags.Instance | BindingFlags.NonPublic);renderPageCallbackMethodInfo = pageRequestManagerType.GetMethod("RenderPageCallback", BindingFlags.Instance | BindingFlags.NonPublic);}public static AjaxFileUploadHelper GetCurrent(Page page){return page.Items[typeof(AjaxFileUploadHelper)] as AjaxFileUploadHelper;}private bool isInAjaxUploading = false;protected override void OnInit(EventArgs e){base.OnInit(e);if (this.Page.Items.Contains(typeof(AjaxFileUploadHelper))){throw new InvalidOperationException("One AjaxFileUploadHelper per page.");}this.Page.Items[typeof(AjaxFileUploadHelper)] = this;this.EnsureIsInAjaxFileUploading();}private void EnsureIsInAjaxFileUploading(){this.isInAjaxUploading =             AjaxFileUploadUtility.IsInIFrameAsyncPostBack(this.Page.Request.Params);if (this.isInAjaxUploading){isInAsyncPostBackFieldInfo.SetValue(ScriptManager.GetCurrent(this.Page),true);this.Page.Error += new EventHandler(Page_Error);}}private void Page_Error(object sender, EventArgs e){// ...}private object _PageRequestManager;private object PageRequestManager{get{if (this._PageRequestManager == null){this._PageRequestManager = pageRequestManagerPropertyInfo.GetValue(ScriptManager.GetCurrent(this.Page), null);}return this._PageRequestManager;}}// ...
}

注册脚本文件

public bool SupportAjaxUpload
{get { return _SupportAjaxUpload; }set { _SupportAjaxUpload = value; }
}
protected override void OnPreRender(EventArgs e)
{base.OnPreRender(e);if (this.isInAjaxUploading){this.Page.SetRenderMethodDelegate(new RenderMethod(this.RenderPageCallback));}if (this.Page.IsPostBack || !this.SupportAjaxUpload) return;if (!ScriptManager.GetCurrent(this.Page).IsInAsyncPostBack){ScriptReference script = new ScriptReference("Jeffz.Web.AjaxFileUploadHelper.js", this.GetType().Assembly.FullName);ScriptManager.GetCurrent(this.Page).Scripts.Add(script);}
}

关闭AJAX上传支持

AjaxFileUploadHelper.GetCurrent(this.Page).SupportAjaxUpload = false;

截获输出方式

if (this.isInAjaxUploading)
{this.Page.SetRenderMethodDelegate(new RenderMethod(this.RenderPageCallback));
}

自定义的输出方法

private void RenderPageCallback(HtmlTextWriter writer, Control pageControl)
{AjaxFileUploadUtility.WriteScriptBlock(this.Page.Response, true);StringBuilder sb = new StringBuilder();HtmlTextWriter innerWriter = new HtmlTextWriter(new StringWriter(sb));renderPageCallbackMethodInfo.Invoke(this.PageRequestManager, new object[] { innerWriter, pageControl });writer.Write(sb.Replace("*/", "*//*").ToString());AjaxFileUploadUtility.WriteScriptBlock(this.Page.Response, false);
}
private void Page_Error(object sender, EventArgs e)
{AjaxFileUploadUtility.WriteScriptBlock(this.Page.Response, true);onPageErrorMethodInfo.Invoke(this.PageRequestManager, new object[] { sender, e });AjaxFileUploadUtility.WriteScriptBlock(this.Page.Response, false);
}