How do I measure the size of a TextBlock in WPF before it is rendered?

Question

I have a WPF DataTemplate with two TextBlock controls (stacked) and then some other elements underneath. Due to some complicated layout code, I need to know the height of the two TextBlock elements so that I can draw some fancy connector lines, and line up other controls, etc.

If I know the text that's going into the TextBlocks, and I know the font, etc., is there some way I can compute or measure the height of these TextBlocks without actually rendering them?

Answer 1

I think it should be sufficient to call the UIElement.Measure(Size) method and subsequently check the UIElement.DesiredSize property. For more information, check the provided MSDN links.

Answer 2

The call to UIElement.Measure(Size), takes as a parameter Size. The second call UIElement.DesiredSize returns whatever Size you passed into the Measure method.

I think this is the case because UIElement (TextBlock in this case) is NOT a child of any control (yet) and therefore DesiredSize has no reason to be anything different.

Answer 3

I appreciate that this is a rather old question, but I have found that using the following code

        TextBlock textBlock = new TextBlock();
        textBlock.Text = "NR valve";
        Size msrSize = new Size(100, 200);
        textBlock.Measure(msrSize);
        Size dsrdSize = textBlock.DesiredSize;

dsrdSize is returned as {47.05,15.96}. The trick seems to be making the msrSize larger than the expected actual size. msrSize seems to act as a limit for the DesiredSize() result. For example, using msrSize = new Size(10, 10), results in a dsrdSize of {10,10} here. Hope this helps someone.

Answer 4

public static Size ShapeMeasure(TextBlock tb) {
    // Measured Size is bounded to be less than maxSize
    Size maxSize = new Size(
         double.PositiveInfinity, 
         double.PositiveInfinity);
    tb.Measure(maxSize);
    return tb.DesiredSize;
}

public static Testit() 
{
    TextBlock textBlock = new TextBlock();
    textBlock.Text = "NR valve";

    Size text size = ShapeMeasure(textBlock);
}