In my code privatefontcollection not able to dispose the object

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C#6.0

Hi ,
when i loading the external font using c# language getting following error

Quote:

error:- System.Runtime.InteropServices.SEHException: 'External component has thrown an exception

Below is my code

private float MeasureString(string fontName, float fontSize, string text)
        {
            const float offSet = -20f;

            var fontFamily = GetFontFamily(fontName);
            var font = new Font(fontFamily, fontSize, FontStyle.Regular, GraphicsUnit.Millimeter);
            var bitmap = new Bitmap(1, 1);
            bitmap.SetResolution(96.0f, 96.0f);
            using(var graphic = Graphics.FromImage(bitmap))
            {
                graphic.PageUnit = GraphicsUnit.Millimeter;
                var size = graphic.MeasureString(text, font, new PointF(0, 0), new StringFormat(StringFormatFlags.FitBlackBox | StringFormatFlags.DirectionRightToLeft));
                return size.Width + offSet;
            }
            
        }

Loading the functions

private FontFamily GetPrivateFontFamily(string fontName)
        {
            PrivateFontCollection privateFonts = new PrivateFontCollection();
            var directoryPath = _fontFamilySetting.Value.DirectoryPath;
            if (!string.IsNullOrEmpty(directoryPath) && Directory.Exists(directoryPath))
            {
                foreach (string file in Directory.EnumerateFiles(_fontFamilySetting.Value.DirectoryPath))
                {
                    privateFonts.AddFontFile(file);
                }
                return privateFonts.Families.First(f => f.Name == fontName);
            }
            return null;
        }

Can anyone please help us to solve the error

What I have tried:

Yes, i tried the code using(var graphic = Graphics.FromImage(bitmap)) statement where by using the statement automatically object release but it wont happening in my code