我如何在任何我想要的地方向响应流中插入一个字符串?

要做到这一点,您必须实现自己的流对象,并将其用作响应的过滤器。

为:

public class TimerStream : Stream
{
    private Stream inner { get; set; }
    private StringBuilder   responseHtml;

    public TimerStream(Stream inputStream) { 
        inner = inputStream; 
        responseHtml = new StringBuilder();
        // Setup your timer
    }

    /* Filter overrides should pass through to inner, all but Write */
    public override void Write(byte[] buffer, int offset, int count)
    {
        string bufferedHtml = System.Text.UTF8Encoding.UTF8.GetString (buffer, offset, count);
        Regex endTag = new Regex ("</html>", RegexOptions.IgnoreCase);

        if (!endTag.IsMatch (bufferedHtml))
        {
            responseHtml.Append(bufferedHtml);
        }
        else
        {
            // insert timer html into buffer, then...
            responseHtml.Append (bufferedHtml);
            byte[] data = System.Text.UTF8Encoding.UTF8.GetBytes (responseHtml.ToString ());            
            inner.Write (data, 0, data.Length);            
        }
    }
}

然后,在httpmodule中,将此添加到beginrequest中:

// Change the Stream filter
HttpResponse response = context.Response;
response.Filter = new TimerStream(context.Response.Filter);