public static class FruitCode
{
public const int Apple = 0x00080020;
public const int Banana = 0x00080021;
public const int Orange = 0x00080022;
}

Type t = typeof(FruitCode);
FieldInfo[] fis = t.GetFields(); // 注意，这里不能有任何选项，否则将无法获取到const常量
Dictionary<int, string> dicFruitCode = new Dictionary<int, string>();
foreach (var fieldInfo in fis)
{
var codeValue = fieldInfo.GetRawConstantValue();
dicFruitCode.Add(Convert.ToInt32(codeValue), fieldInfo.Name.ToString());
}

foreach(var item in dicFruitCode)
{
Console.WriteLine("FieldName:{0}={1}",item.Value,item.Key);
}