Question

I have a LINQ expression that’s slowing down my application.
I’m drawing a control, but to do this, I need to know the max width of the text that will appear in my column.

The way I’m doing that is this:

return Items.Max(w => TextRenderer.MeasureText((w.RenatlUnit == null)? "" : 
w.RenatlUnit.UnitNumber, this.Font).Width) + 2;

However, this iterates over ~1000 Items, and takes around 20% of the CPU time that is used in my drawing method. To make it worse, there are two other columns that this must be done with, so this LINQ statement on all the items/columns takes ~75-85% of the CPU time.

TextRenderer is from System.Windows.Forms package, and because I’m not using a monospaced font, MeasureText is needed to figure out the pixel width of a string.

How might I make this faster?

Answer 1

I don’t believe that your problem lies in the speed of LINQ, it lies in the fact that you’re calling MeasureText over 1000 times. I would imagine that taking your logic out of a LINQ query and putting it into an ordinary foreach loop would yield similar run times.

A better idea is probably to employ a little bit of sanity checking around what you’re doing. If you go with reasonable inputs (and disregard the possibility of linebreaks), then you really only need to measure the text of strings that are, say, within 10% or so of the absolute longest (in terms of number of characters) string, then use the maximum value. In other words, there’s no point in measuring the string “foo” if the largest value is “paleontology”. There’s no font that has widths THAT variable.