Kan - Microsoft Apple Google

namespace MyProject.Extensions
{

public static class StringExtension
{
    // FontSize : 0 will not apply size calculation
    // FontFamily: null will not apply size calculation
    // FontWeight is not nullable, default use FontWeights.Normal
    public static Size Measure(this string strText, double dbFontSize, FontFamily fontFamily, FontWeight fontWeight)
    {
        var tb = new TextBlock();
        if (dbFontSize > 0)
            tb.FontSize = dbFontSize;

        if (fontFamily != null)
            tb.FontFamily = fontFamily;

        tb.FontWeight = fontWeight;
            tb.Text = strText;

        var tb2 = tb;
        return new Size(tb2.ActualWidth, tb2.ActualHeight);
    }
}

}   

Usage:
   string strTest = "9999";
   Size size = strTest.Measure(12, new FontFamily("Tahoma"), FontWeights.Normal);
   ctrlAA.Height = size.Height;