var file = ImageFile.FromFile("path_to_image");

// the type of the ISO speed rating tag value is unsigned short
// see documentation for tag data types
var isoTag = file.Properties.Get<ExifUShort>(ExifTag.ISOSpeedRatings);

// the flash tag's value is an enum
var flashTag = file.Properties.Get<ExifEnumProperty<Flash>>(ExifTag.Flash);

// GPS latitude is a custom type with three rational values
// representing degrees/minutes/seconds of the latitude 
var latTag = file.Properties.Get<GPSLatitudeLongitude>(ExifTag.GPSLatitude);

var file = ImageFile.FromFile("path_to_image");
// note the explicit cast to ushort
file.Properties.Set(ExifTag.ISOSpeedRatings, <ushort>200);

file.Save("path_to_image");