How do you underline text with dashedline in ITEXT PDF - itext

Question

I have underlined "Some text" by
var par = new Paragraph();
par.Add(new Chunk("Some text", CreateFont(12, Font.UNDERLINE)));
document.Add(par);
It is possible underline just "Some text" with dashed line (not the paragraph)?
Thanks

Answer 1

This answer tells you how to do it but unfortunately doesn't provide any code so I've provided it below.
To the best on my knowledge there isn't a direct way to achieve this in iTextSharp by just setting a simple property. Instead, you need to use a PageEvent and manually draw the line yourself.
First you need to subclass PdfPageEventHelper:
private class UnderlineMaker : PdfPageEventHelper {
}
You then want to override the OnGenericTag() method:
public override void OnGenericTag(PdfWriter writer, Document document, iTextSharp.text.Rectangle rect, string text) {
}
The text variable will hold an arbitrary value that you set later on. Here's a full working example with comments:
private class UnderlineMaker : PdfPageEventHelper {
public override void OnGenericTag(PdfWriter writer, Document document, iTextSharp.text.Rectangle rect, string text) {
switch (text) {
case "dashed":
//Grab the canvas underneath the content
var cb = writer.DirectContentUnder;
//Save the current state so that we don't affect future canvas drawings
cb.SaveState();
//Set a line color
cb.SetColorStroke(BaseColor.BLUE);
//Set a dashes
//See this for more details: http://api.itextpdf.com/itext/com/itextpdf/text/pdf/PdfContentByte.html#setLineDash(float)
cb.SetLineDash(3, 2);
//Move the cursor to the left edge with the "pen up"
cb.MoveTo(rect.Left, rect.Bottom);
//Move to cursor to the right edge with the "pen down"
cb.LineTo(rect.Right, rect.Bottom);
//Actually draw the lines (the "pen downs")
cb.Stroke();
//Reset the drawing states to what it was before we started messing with it
cb.RestoreState();
break;
}
//There isn't actually anything here but I always just make it a habit to call my base
base.OnGenericTag(writer, document, rect, text);
}
}
And below is an implementation of it:
//Create a test file on the desktop
var testFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "test.pdf");
//Normal iTextSharp boilerplate, nothing special here
using (var fs = new FileStream(testFile, FileMode.Create, FileAccess.Write, FileShare.None)) {
using (var doc = new Document()) {
using (var writer = PdfWriter.GetInstance(doc, fs)) {
doc.Open();
//Bind our helper class
writer.PageEvent = new UnderlineMaker();
//Create a new paragraph
var p = new Paragraph();
//Add a normal chunk
p.Add(new Chunk("This is a "));
//Create another chunk with an arbitrary tag associated with it and add to the paragraph
var c = new Chunk("dashed underline test");
c.SetGenericTag("dashed");
p.Add(c);
//Add the paragraph to the document
doc.Add(p);
doc.Close();
}
}
}
If you wanted to get fancy you could pass a delimited string to SetGenericTag() like dashed-black-2x4 or something and parse that out in the OnGenericTag event.