让UpdatePanel支持文件上传（2）：服务器端组件

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;
        }
        
    }
    // ...
}

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;
        }
    }
    // ...
}

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);
    }
}

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

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

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);
}