private static void SetRecordWriter(this HtmlHelper html, RecordWriter writer)
{
RecordWriter existWriter = html.ViewContext.HttpContext.Items[RecordWriterKey] as RecordWriter;
if (existWriter != null)
{
throw new InvalidOperationException("RecordWriter 已经存在，可能页面已经被缓存了");
}
html.ViewContext.HttpContext.Items[RecordWriterKey] = writer;
}
/// <summary>
/// 创建用于片断缓存的 <see cref="RecordWriter"/>
/// </summary>
/// <param name="html"></param>
/// <param name="writer"></param>
/// <returns></returns>
public static TextWriter CreateCacheWriter(this HtmlHelper html, TextWriter writer)
{
RecordWriter recordWriter = new RecordWriter(writer);
html.SetRecordWriter(recordWriter);
return recordWriter;
}