public delegate void ReleasePageStream(
	int pageNumber,
	Stream pageStream
)

Public Delegate Sub ReleasePageStream ( 
	pageNumber As Integer,
	pageStream As Stream
)

public delegate void ReleasePageStream(
	int pageNumber, 
	Stream^ pageStream
)

type ReleasePageStream = 
    delegate of 
        pageNumber : int * 
        pageStream : Stream -> unit

CreatePageStream createDelegate = delegate (int pageNumber)
{
    var pagePath = System.IO.Path.Combine(@"C:\Temp", string.Format("page_{0}.png", pageNumber));
    return System.IO.File.Create(pagePath);
};
ReleasePageStream releaseDelegate = delegate (int pageNumber, System.IO.Stream pageStream)
{
    // do anything with Stream, containing page preview
    pageStream.Close();
};
var previewOptions = new PreviewOptions(createDelegate, releaseDelegate);
previewOptions.PreviewFormat = PreviewOptions.PreviewFormats.PNG;
previewOptions.Height = 640;
previewOptions.Width = 480;
previewOptions.PageNumbers = new int[] { 1 };
using (var redactor = new Redactor("C:\Temp\SourceFile.pdf"))
{
    redactor.GeneratePreview(previewOptions);
}