Develop Reference

How can i convert a file .png to a Bitmap? Nothing works for me. Error "'Failed to decode image. The provided image must be a Bitmap.'" Xamarin.forms

I'm working with Xamarin in the part of Xamarin.Forms i need to convert a file ("image.png") to a Bitmap because when project run its enter in "break mode" and show me this message "Java.Lang.IllegalArgumentException: 'Failed to decode image. The provided image must be a Bitmap.'". So i tried to convert the file in many ways like:
1_ Using methods from System.Drawing.Bitmap but it's show this exception "This operation is not supported in this platform"
2_ Cannot use Android.Graphics because i'm working in xamarin.forms not in xamarin.android.
3_ I tried to convert the "image.png" into a base64 or byte[] array and then into a bitmap but the problem is the same like in first problem because to convert from byte[] array or base64 to a Bitmap i have use methods from System.Drawing.Bitmap.
4_ I tried using the library SkiaSharp but i don't have success because i don't found so much information about how to convert .png to SKBitmap and then convert SKBitmap to Bitmap (even i don't know if this is possible).
5_ Finally i converted "image.png" to a "image.bmp" with an app and use the file .bmp in my project but it doesn't work too.
the "image.png" i have to save in a string variable, well that's the idea.
If you have a solution with SkiaSharp o whatever i will glad
EDIT
here is a part of my code, i just save in a variable the image
Icon = "pin_blue.png";
//i can't use a path because in xamarin you have many size from the same
//image for the different size of the screen
EDIT 2 This is my method to show the pins in google maps
private void ShowPins(List<PointsOfInterest> resultPointsOfInterest)
{
if (resultPointsOfInterest != null && resultPointsOfInterest.Any())
{
var location = Geolocation.GetLastKnownLocationAsync();
PointsOfInterest position = new PointsOfInterest();
if (location != null)
{
position.ccsm0166latitud = location.Result.Latitude;
position.ccsm0166longitud = location.Result.Longitude;
}
else {
position = resultPointsOfInterest.First();
}
//Distance = Distance.FromKilometers(new Random().Next(23,35));
Distance = Distance.FromKilometers(3);
Position = new Position(position.ccsm0166latitud, position.ccsm0166longitud);
PinsFiltered= Pins = new List<PinCustom>(resultPointsOfInterest.Select(
x => new PinCustom()
{
Position =
new Position(x.ccsm0166latitud, x.ccsm0166longitud),
Address = x.ccsm0166direccion,
Label = x.ccsm0166nombre,
Type = PinType.Place,
TypePointOfInterest = x.ccsm0166tipositio,
IconBM = Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branch ? PinCustom.ConvertToBitmap("pin_blue.png") :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branch ? "pin_blue.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours2 ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours3 ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.selfServiceTerminal ? "pin_green.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.atmServBox ? "pin_yellow.png" : string.Empty
}).ToList());
}
else
{
Pins = new List<PinCustom>();
}
}
This is the class Pin where i save the image
public class PinCustom : Pin
{
public string TypePointOfInterest { get; set; }
public string Icon { get; set; }
public Bitmap { get; set; }
//Here i create this variable to save a bitmap but i don't know if i do the things well
}
this is the icon .png i want to show in googlemaps
Pin Blue Image

To open your file and convert it to byte array:
string directory = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, Android.OS.Environment.DirectoryDownloads);
// or your image directory, just replace it
var stream = File.OpenWrite(Path.Combine(directory, "image.png"));
byte[] buff = ConvertStreamToByteArray(stream);
stream.Close();
public static byte[] ConvertStreamToByteArray(Stream stream)
{
byte[] byteArray = new byte[16 * 1024];
using (MemoryStream mStream = new MemoryStream())
{
int bit;
while ((bit = stream.Read(byteArray, 0, byteArray.Length)) > 0)
{
mStream.Write(byteArray, 0, bit);
}
return mStream.ToArray();
}
}
then, to pass this byte array to SKBitmap:
SKBitmap bmp = SKBitmap.Decode(buff);
EDIT:
If you want to try without ConvertStreamToByteArray():
byte[] buff = null;
stream.Write(buff, 0, buff.Length);
This Write will depend of the type of your stream. In this example, I'm using FileStream.
EDIT 2:
string resourceID = "image.png";
Assembly assembly = GetType().GetTypeInfo().Assembly;
using (Stream stream = assembly.GetManifestResourceStream(resourceID))
{
resourceBitmap = SKBitmap.Decode(stream);
SKBitmap bmp = SKImage.FromBitmap(resourceBitmap);
}
and then you can use this bitmap to draw and fill your SKCanvas:
canvas.DrawBitmap(bmp, 0, 0);

Use ffmpeg
command for this: ffmpeg -i image.png image.bmp

i have 5 types of pins (pins are the image .png) when i put the pins
in format .png
if you want to custom the pins in your map, you can simply use Custom Renderers to achieve this.
The icon used to represent a marker can be customized by calling the MarkerOptions.SetIcon method. This can be accomplished by overriding the CreateMarker method, which is invoked for each Pin that's added to the map:
protected override MarkerOptions CreateMarker(Pin pin)
{
var marker = new MarkerOptions();
marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
marker.SetTitle(pin.Label);
marker.SetSnippet(pin.Address);
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.pin));
return marker;
}
If you want to display different icons, you can refer to the following code:
protected override MarkerOptions CreateMarker(Pin pin)
{
var marker = new MarkerOptions();
marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
marker.SetTitle(pin.Label);
marker.SetSnippet(pin.Address);
var customPin = (Element as CustomMap).CustomPins.FirstOrDefault(p => p.Position == pin.Position);
if (customPin != null)
{
if (customPin.IconType == "corporate")
{
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.corporate));
}
else if (customPin.IconType == "pickup")
{
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.bus));
}
}
return marker;
}
For more, check:Customizing the Marker.

IText7 PDFHtml generator with header and footer for C#

I am trying to generating a PDF from predefined HTML content. I managed to generate the content, yet without the required HTML Header, HTML Footer, and Arabic language is not supported as well.
My requirements:
Arabic language support.
The ability to generate more than 10 pages.
The footer may differ from one page to another.
There is a web application that sends a request to a WCF service, and the service returns a byte array containing the PDF.
So, I have been searching for a couple of days for a good tool and I found SelectPdf, it is perfect except that it is NOT free, so the only solution is IText7 PDFHtml.
The thing is this library has good documentation for JAVA, and I am really struggling in following the C# examples and converting from JAVA API to C# code.
Anyone has done something similar before with c#?

After a long process of searching and trying, I have got it working and achieved the following features:
Image in the header.
Base64 image in the footer, in addition to the ability to write some text in the other side in the footer.
Generating the same footer for all pages except for the last one.
the number of the generated pages was unlimited.
Page numbering.
All the previous features were free of charge, however, supporting Arabic language needs a license, so I have to pay anyway :)
Kindly find below my C# code and post your improvements if you have any.
public class Pdfgenerator
{
public const string FONT = "Fonts/NotoNaskhArabic-Regular2.ttf";
public static string HEADER_TEXT = "<table width=\"100%\" border=\"0\"><tr><td>Header</td><td align=\"right\">Some title</td></tr></table>";
public static string FOOTER_TEXT = "<table width=\"100%\" border=\"0\"><tr><td>Footer</td><td align=\"right\">Some title</td></tr></table>";
public MemoryStream createPdf()
{
string apPath = System.Web.Hosting.HostingEnvironment.ApplicationPhysicalPath;
MemoryStream file = new MemoryStream();
PdfDocument pdfDocument = null;
PdfDocument pdfDoc = null;
PdfDocument pdfDocument1 = null;
try
{
using (file)
{
PdfFont f = PdfFontFactory.CreateFont(apPath + FONT, PdfEncodings.IDENTITY_H);
string header = "pdfHtml Header and footer example using page-events";
Header headerHandler = new Header(header);
Footer footerHandler = new Footer();
ConverterProperties converterProperties = new ConverterProperties();
PdfWriter writer1 = new PdfWriter(apPath + "test1.pdf");
pdfDocument1 = new PdfDocument(writer1);
pdfDocument1.AddEventHandler(PdfDocumentEvent.START_PAGE, headerHandler);
pdfDocument1.AddEventHandler(PdfDocumentEvent.END_PAGE, footerHandler);
converterProperties = new ConverterProperties().SetBaseUri(apPath);
HtmlConverter.ConvertToDocument(File.ReadAllText(apPath + "content.html"), pdfDocument1, converterProperties);
footerHandler.lastPage = pdfDocument1.GetLastPage();
pdfDocument1.Close();
}
}
catch (Exception ex)
{
}
finally
{
file.Dispose();
}
return new MemoryStream();
}
}
Generating the header:
class Header : IEventHandler
{
private string header;
private Image image;
public Header(string header)
{
string apPath = System.Web.Hosting.HostingEnvironment.ApplicationPhysicalPath;
this.header = header;
image = new Image(ImageDataFactory.Create(apPath + "Images/RANDOM_PHOTO.jpg"));
}
public void HandleEvent(Event #event)
{
PdfDocumentEvent docEvent = (PdfDocumentEvent)#event;
PdfDocument pdf = docEvent.GetDocument();
PdfPage page = docEvent.GetPage();
Rectangle pageSize = page.GetPageSize();
Canvas canvas = new Canvas(new PdfCanvas(page), pdf, pageSize);
canvas.SetFontSize(18);
// Write text at position
canvas.Add(image);
canvas.Close();
}
}
Generating the footer:
class Footer : IEventHandler
{
public PdfPage lastPage = null;
protected PdfFormXObject placeholder;
protected float side = 20;
protected float x = 300;
protected float y = 25;
protected float space = 4.5f;
protected float descent = 3;
public Footer()
{
placeholder = new PdfFormXObject(new Rectangle(0, 0, side, side));
}
public void HandleEvent(Event #event)
{
PdfDocumentEvent docEvent = (PdfDocumentEvent)#event;
PdfDocument pdf = docEvent.GetDocument();
PdfPage page = docEvent.GetPage();
int pageNumber = pdf.GetPageNumber(page);
Rectangle pageSize = page.GetPageSize();
// Creates drawing canvas
PdfCanvas pdfCanvas = new PdfCanvas(page);
Canvas canvas = new Canvas(pdfCanvas, pdf, pageSize);
IList<iText.Layout.Element.IElement> elements = HtmlConverter.ConvertToElements("<table border=\"0\"><tr><td><img src=\"data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==\" alt=\"Italian Trulli\"></td></tr></table>");
Paragraph p = new Paragraph();
foreach (iText.Layout.Element.IElement e in elements)
{
if (e is IBlockElement) {
p.Add((IBlockElement)e);
}
}
if (lastPage == docEvent.GetPage()) {
}
else
{
canvas.ShowTextAligned(p, 25, 75, TextAlignment.LEFT);
}
canvas.Close();
// Create placeholder object to write number of pages
pdfCanvas.AddXObject(placeholder, x + space, y - descent);
pdfCanvas.Release();
}
public void writeTotal(PdfDocument pdf)
{
Canvas canvas = new Canvas(placeholder, pdf);
canvas.ShowTextAligned(pdf.GetNumberOfPages().ToString(),
0, descent, TextAlignment.LEFT);
canvas.Close();
}
}
I was trying to get a stream as an output, so if you want that as well you can use the following in your main service:
public byte[] GetData()
{
MemoryStream stream = new Pdfgenerator().createPdf();
byte[] arr = stream.ToArray();
return stream.ToArray();
}

C# Pdf to Text with image placeholder

I have a batch of PDFs that I want to convert to Text. It's easy to get text with something like this from iTextSharp:
PdfTextExtractor.GetTextFromPage(reader, pageNumber);
It's easy to get Images using this answer (or similar answers in the thread).
What I can't figure out easily... is how to interleave image placeholders in the text.
Given a PDF, a page # and GetTextFromPage I expect the output to be:
line 1
line 2
line 3
When I'd like it to be (Where 1.1 means page 1, image 1... Page 1, image 2):
line 1
[1.1]
line 2
[1.2]
line 3
Is there a way to get an "image placeholder" for iTextSharp, PdfSharp or anything similar? I'd like a GetTextAndPlaceHoldersFromPage method (or similar).
PS: Hrm... it's not letting me tag iTextSHARP - not iText. C# not Java.

C# Pdf to Text with image placeholder
https://stackoverflow.com/a/28087521/
https://stackoverflow.com/a/33697745/
Although this doesn't have the exact layout mentioned in my question (Since that was a simplified version of what I really wanted anyways), it does have the starting parts as listed by the second note (translated from iText Java)... with extra information pulled from the third note (Some of the reflection used in Java didn't seem to work in C#, so that info came from #3).
Working from this, I'm able to get a List of Strings representing lines in the PDF (all pages, instead of just page 1)... with text added where images should be (Huzzah!). ByteArrayToFile extension method added for flavor (Although I didn't include other parts/extensions that may break a copy/paste usages of this code).
I've also been able to greatly simplify other parts of my process and gut half of the garbage I had working before. Huzzah!!! Thanks #Mkl
internal class Program
{
public static void Main(string[] args)
{
var dir = Settings.TestDirectory;
var file = Settings.TestFile;
Log.Info($"File to Process: {file.FullName}");
using (var reader = new PdfReader(file.FullName))
{
var parser = new PdfReaderContentParser(reader);
var listener = new SimpleMixedExtractionStrategy(file, dir);
parser.ProcessContent(1, listener);
var x = listener.GetResultantText().Split('\n');
}
}
}
public class SimpleMixedExtractionStrategy : LocationTextExtractionStrategy
{
public static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
public DirectoryInfo OutputPath { get; }
public FileInfo OutputFile { get; }
private static readonly LineSegment UNIT_LINE = new LineSegment(new Vector(0, 0, 1), new Vector(1, 0, 1));
private int _counter;
public SimpleMixedExtractionStrategy(FileInfo outputFile, DirectoryInfo outputPath)
{
OutputPath = outputPath;
OutputFile = outputFile;
}
public override void RenderImage(ImageRenderInfo renderInfo)
{
try
{
var image = renderInfo.GetImage();
if (image == null) return;
var number = _counter++;
var imageFile = new FileInfo($"{OutputFile.FullName}-{number}.{image.GetFileType()}");
imageFile.ByteArrayToFile(image.GetImageAsBytes());
var segment = UNIT_LINE.TransformBy(renderInfo.GetImageCTM());
var location = new TextChunk("[" + imageFile + "]", segment.GetStartPoint(), segment.GetEndPoint(), 0f);
var locationalResultField = typeof(LocationTextExtractionStrategy).GetField("locationalResult", BindingFlags.NonPublic | BindingFlags.Instance);
var LocationalResults = (List<TextChunk>)locationalResultField.GetValue(this);
LocationalResults.Add(location);
}
catch (Exception ex)
{
Log.Debug($"{ex.Message}");
Log.Verbose($"{ex.StackTrace}");
}
}
}
public static class ByteArrayExtensions
{
public static bool ByteArrayToFile(this FileInfo fileName, byte[] byteArray)
{
try
{
// Open file for reading
var fileStream = new FileStream(fileName.FullName, FileMode.Create, FileAccess.Write);
// Writes a block of bytes to this stream using data from a byte array.
fileStream.Write(byteArray, 0, byteArray.Length);
// close file stream
fileStream.Close();
return true;
}
catch (Exception exception)
{
// Error
Log.Error($"Exception caught in process: {exception.Message}", exception);
}
// error occured, return false
return false;
}
}

Render a barcode in ASP.NET Web Form

i am trying to show the barcode in asp.net page. already download the zen barcode render with sample code. i tried the sample it is working fine with me. once i try in my code barcode label is showing empty. i checked with sample code and mine i did not find any difference , only data transfer is the different. this is what i tried.
<barcode:BarcodeLabel ID="BarcodeLabel1" runat="server" BarcodeEncoding="Code39NC" LabelVerticalAlign="Bottom" Text="12345"></barcode:BarcodeLabel>
if (!IsPostBack)
{
List<string> symbologyDataSource = new List<string>(
Enum.GetNames(typeof(BarcodeSymbology)));
symbologyDataSource.Remove("Unknown");
barcodeSymbology.DataSource = symbologyDataSource;
barcodeSymbology.DataBind();
}
this is the function
BarcodeSymbology symbology = BarcodeSymbology.Unknown;
if (barcodeSymbology.SelectedIndex != 0)
{
symbology = (BarcodeSymbology)1;
}
symbology = (BarcodeSymbology)1;
string text = hidID.Value.ToString();
string scaleText = "1";
int scale;
if (!int.TryParse(scaleText, out scale))
{
if (symbology == BarcodeSymbology.CodeQr)
{
scale = 3;
}
else
{
scale = 1;
}
}
else if (scale < 1)
{
scale = 1;
}
if (!string.IsNullOrEmpty(text) && symbology != BarcodeSymbology.Unknown)
{
barcodeRender.BarcodeEncoding = symbology;
barcodeRender.Scale = 1;
barcodeRender.Text = text;
}
symbology is set as Code39NC from the dropdown. scale is 1 and text is coming from other form the value is passing as well. still the bacodelable is showing only value not the barcode picture.

Here are two code samples using ZXing to create a (QR) barcode as both an image and as a base64 encoded string. Both of these options can be used with an <img /> tag to embed the barcode in the page.
This is not an ASP.NET control. It is a library that creates barcodes from text.
// First Text to QR Code as an image
public byte[] ToQRAsGif(string content)
{
var barcodeWriter = new BarcodeWriter
{
Format = BarcodeFormat.QR_CODE,
Options = new EncodingOptions
{
Height = this._h,
Width = this._w,
Margin = 2
}
};
using (var bitmap = barcodeWriter.Write(content))
using (var stream = new MemoryStream())
{
bitmap.Save(stream, ImageFormat.Gif);
stream.Position = 0;
return stream.GetBuffer();
}
}
// From Text to QR Code as base64 string
public string ToQRAsBase64String(string content)
{
var barcodeWriter = new BarcodeWriter
{
Format = BarcodeFormat.QR_CODE,
Options = new EncodingOptions
{
Height = _h,
Width = _w,
Margin = 2
}
};
using (var bitmap = barcodeWriter.Write(content))
using (var stream = new MemoryStream())
{
bitmap.Save(stream, ImageFormat.Gif);
return String.Format("data:image/gif;base64,{0}", Convert.ToBase64String(stream.ToArray()));
}
}
Hope this helps! Happy coding.
UPDATE: Here is the link to their product page on codeplex: https://zxingnet.codeplex.com/

How to Print Preview when using a DocumentPaginator to print?

I'm using a class I've derived from DocumentPaginator (see below) to print simple (text only) reports from a WPF application. I've got it so that everything prints correctly, But how do I get it to do a print preview before printing? I have a feeling I need to use a DocumentViewer but I can't figure out how.
Here's my Paginator Class:
public class RowPaginator : DocumentPaginator
{
private int rows;
private Size pageSize;
private int rowsPerPage;
public RowPaginator(int rows)
{
this.rows = rows;
}
public override DocumentPage GetPage(int pageNumber)
{
int currentRow = rowsPerPage * pageNumber;
int rowsToPrint = Math.Min(rowsPerPage, rows - (rowsPerPage * pageNumber - 1));
var page = new PageElementRenderer(pageNumber + 1, PageCount, currentRow, rowsToPrint)
{
Width = PageSize.Width,
Height = PageSize.Height
};
page.Measure(PageSize);
page.Arrange(new Rect(new Point(0, 0), PageSize));
return new DocumentPage(page);
}
public override bool IsPageCountValid { get { return true; } }
public override int PageCount { get { return (int)Math.Ceiling(this.rows / (double)this.rowsPerPage); } }
public override Size PageSize
{
get { return this.pageSize; }
set
{
this.pageSize = value;
this.rowsPerPage = PageElementRenderer.RowsPerPage(this.pageSize.Height);
if (rowsPerPage <= 0)
throw new InvalidOperationException("Page can't fit any rows!");
}
}
public override IDocumentPaginatorSource Source { get { return null; } }
}
The PageElementRenderer is just a simple UserControl that displays the data (at the moment just a list of rows).
Here's how I use my Row Paginator
PrintDialog dialog = new PrintDialog();
if (dialog.ShowDialog() == true)
{
var paginator = new RowPaginator(rowsToPrint) { PageSize = new Size(dialog.PrintableAreaWidth, dialog.PrintableAreaHeight) };
dialog.PrintDocument(paginator, "Rows Document");
}
Sorry for the code dump, but I didn't want to miss something relevant.

So I got it working after reading Pro WPF in C# 2008 (Page 726).
Basically the DocumentViewer class needs an XPS file to present a print preview of it. So I do the following:
PrintDialog dialog = new PrintDialog();
var paginator = new RowPaginator(rowsToPrint) { PageSize = new Size(dialog.PrintableAreaWidth, dialog.PrintableAreaHeight) };
string tempFileName = System.IO.Path.GetTempFileName();
//GetTempFileName creates a file, the XpsDocument throws an exception if the file already
//exists, so delete it. Possible race condition if someone else calls GetTempFileName
File.Delete(tempFileName);
using (XpsDocument xpsDocument = new XpsDocument(tempFileName, FileAccess.ReadWrite))
{
XpsDocumentWriter writer = XpsDocument.CreateXpsDocumentWriter(xpsDocument);
writer.Write(paginator);
PrintPreview previewWindow = new PrintPreview
{
Owner = this,
Document = xpsDocument.GetFixedDocumentSequence()
};
previewWindow.ShowDialog();
}
I'm creating the print dialog to get the default page size. There's probably a better way to do this.
XpsDocument is in ReachFramework.dll (Namespace System.Windows.Xps.Packaging);
Here's the PrintPreview Window.
<Window x:Class="WPFPrintTest.PrintPreview"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Name="previewWindow"
Title="PrintPreview" Height="800" Width="800">
<Grid>
<DocumentViewer Name="viewer"
Document="{Binding ElementName=previewWindow, Path=Document}" />
</Grid>
</Window>
The code behind just has a Document property like so:
public IDocumentPaginatorSource Document
{
get { return viewer.Document; }
set { viewer.Document = value; }
}

The following code uses a MemoryStream to do a print preview.
MemoryStream stream = new MemoryStream();
Package package = Package.Open(stream, FileMode.Create, FileAccess.ReadWrite);
var uri = new Uri(#"memorystream://myXps.xps");
PackageStore.AddPackage(uri, package);
var xpsDoc = new XpsDocument(package);
xpsDoc.Uri = uri;
XpsDocument.CreateXpsDocumentWriter(xpsDoc).Write(paginator);
documentViewer.Document = xpsDoc.GetFixedDocumentSequence();
Remember to use close() and remove package from PackageStore when the print preview is closed.

WPF doesn't come with any built-in Print Preview functionality, if you want to do a print preview, you're going to have to construct it yourself. Fortunately, it's shouldn't be that difficult.
You've already got the pagination code, which creates your DocumentPage objects. These objects contain a Visual, which you can go ahead and display in your UI.
What you'll end up doing, is paginating your entire document, collecting all the DocumentPage objects, then displaying their visuals inside of a scrolling StackPanel or something similar. These are the same DocumentPage objects that you can then send to the printer.

XpsDocument doc = new XpsDocument("filename.xps", FileAccess.Read);
docViewer.Document = doc.GetFixedDocumentSequence();
doc.Close();

The WinForm code for print preview is:
PrintPreviewDialog PrintPreviewDialog = new PrintPreviewDialog();
PrintPreviewDialog.Document = PrintDocument;
PrintPreviewDialog.ShowDialog();
P.s.: The original poster has commented that this is the wrong answer for an WPF application.

I dont think there is a built in way of doing this
Here is how I got it working in NHaml
var documentViewHostDialog = new DocumentDialog();
documentViewHostDialog.LoadDocument(load);
documentViewHostDialog.ShowDialog();
Where "load" is either a FlowDocument or IDocumentPaginatorSource
and here is the DocumentDialog
http://code.google.com/p/nhaml/source/browse/trunk/src/NHaml.Xps/DocumentDialog.xaml
http://code.google.com/p/nhaml/source/browse/trunk/src/NHaml.Xps/DocumentDialog.xaml.cs
Hope it works for your case.