How to measure multi-line text in WPF?

Question

The title really says it all... I need to know how to measure multi-line text in WPF. I really can't believe that this question hasn't already been asked here.

I have found solutions for measuring single line text in WPF (WPF equivalent to TextRenderer), or multi-line text in Windows Forms (C# – Measure String Width & Height (in pixels) Including Multi-line Text), but not multi-line text in WPF. I cannot use the Windows Forms DLL, because I need to measure the strings in a non UI based project, where UI DLLs are not welcome.

To clarify further, what I need is a method, like the Graphics.MeasureString method, that I can pass a set width into, that will return the height in pixels required to render the string in the UI... that can be used without using UI related DLLs.

Answer 1

You may create a FormattedText instance and set its MaxTextWidth property, which makes the text wrap. Then either get the Bounds of its geometry, or perhaps only its height from the Extent property:

var testString = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor";

var formattedText = new FormattedText(
    testString,
    CultureInfo.InvariantCulture,
    FlowDirection.LeftToRight,
    new Typeface("Segoe UI"),
    20,
    Brushes.Black);

formattedText.MaxTextWidth = 200;

var bounds = formattedText.BuildGeometry(new Point(0, 0)).Bounds;
var height = formattedText.Extent;

Not sure however why height and bounds.Height are not exactly equal.