C#/WPF 计算字串的真实长度，调整控件的宽度

下面函数是经常用到的计算字串长度的方法：

private double MeasureTextWidth(String str, string fontName, double fontsize, double width)
        { 
            double width = -1;     
            try
            {
                System.Drawing.Graphics graphics = System.Drawing.Graphics.FromHwnd(m_hWnd);
                graphics.PageUnit = System.Drawing.GraphicsUnit.Point;
                System.Drawing.Font font = new System.Drawing.Font(fontName, (float)fontsize);

System.Drawing.SizeF size = graphics.MeasureString(str, font);

width = size.width;

font.Dispose();
                graphics.Dispose();
            }
            catch (System.Exception e)
            {
            }
            return width;
        }

但是事实上，Graphics.MeasureString并不可靠，在不同的SKU下得到的结果会不同，原因不明，可能跟显卡驱动也会有关系。今天尝试新的方法经测试有效，贡献出来：

private double MeasureTextWidth(string text, double fontSize, string fontFamily)
        {
            FormattedText formattedText = new FormattedText(
            text,
            System.Globalization.CultureInfo.InvariantCulture,
            FlowDirection.LeftToRight,
            new Typeface(fontFamily.ToString()),
            fontSize,
            Brushes.Black
            );
            return formattedText.WidthIncludingTrailingWhitespace;
        }

另，附送枚举已安装字体的方法：

System.Drawing.FontFamily[] fontFamilies;
                InstalledFontCollection installedFontCollection = new InstalledFontCollection();
                fontFamilies = installedFontCollection.Families;

int count = fontFamilies.Length;
                log("fontFamilies.Length=" + fontFamilies.Length);
                for (int i = 0; i < count; i++)
                {
                    fontName = fontFamilies[i].Name;
                    log("fontName: " + fontName);
                }

参考自：http://zwkufo.blog.163.com/blog/static/258825120116663748213/