怎么把DNN的viewstate保存在Disk File?

虽然DNN中有个DiskPageStatePersister,可是在Host Setting中不可以选择，而且我自己测试了下，有Bug,有时候文件名太长了，不能建立文件。那在不该DNN source code的前提下怎么才能把viewstate保存在服务器端呢？ 让我们先研究下DNN的PageBase中的PageStatePersister属性:

Protected Overrides ReadOnly Property PageStatePersister() As System.Web.UI.PageStatePersister
            Get
                'Set ViewState Persister to default (as defined in Base Class)
                Dim _persister As PageStatePersister = MyBase.PageStatePersister
                If Not DotNetNuke.Common.Globals.HostSettings("PageStatePersister") Is Nothing Then
                    Select Case DirectCast(DotNetNuke.Common.Globals.HostSettings("PageStatePersister"), String)
                        Case "M"
                            _persister = New CachePageStatePersister(Me)
                        Case "D"
                            _persister = New DiskPageStatePersister(Me)
                        Case "S"
                            _persister = New SessionPageStatePersister(Me)
                    End Select
                End If
                Return _persister
            End Get
        End Property

从上面的Code中我们看到，DNN只handle "M", "D", "S"这几种，如果把viewstate保存在Page中的话，就会用.Net 默认的PageStaePersister.
接下来，我们打开Reflector看看System.Web.UI.Page是怎么写的：

protected virtual PageStatePersister PageStatePersister
{
    get
    {
        if (this._persister == null)
        {
            PageAdapter pageAdapter = this.PageAdapter;
            if (pageAdapter != null)
            {
                this._persister = pageAdapter.GetStatePersister();
            }
            if (this._persister == null)
            {
                this._persister = new HiddenFieldPageStatePersister(this);
            }
        }
        return this._persister;
    }
}

好了，我们可以看到，原来会先从PageAdapter中拿，如果找不到的话，才会用： HiddenFieldPageStatePersister.
这样我们就可以从PageAdapter下手了。
首先PageApater:

public class HCPageAdapter : PageAdapter
    {
        public override PageStatePersister GetStatePersister()
        {
            return new XmlPageStatePersister(base.Page);
        }
    }

其中： XmlPageStatePersister的任务就是save, Load Viewstate From server disk.
然后的.Browser文件，告诉.Net要加载HCPageAdapter

<browsers>
    <browser refID="Default">
      <controlAdapters>
        <adapter controlType="DotNetNuke.Framework.PageBase"
                 adapterType="HC.DNN.Services.ViewState.HCPageAdapter" />
      </controlAdapters>
    </browser>
</browsers>

Ok, 现在编译，把dll放到bin folder, .Browser文件放到App_browser folder就完成了， 这样即使下载升级DNN也不影响。
你可以从这里下载本文用到的Code: DNN store Viewstate in disk revised