Ok .... this is my final ( and not the best) solution!
I just created another enum ...
[Serializable]
public enum DayOfWeekEnum
{
[EnumMember]
[XmlEnum(Name = "0")]
Sunday = 0,
[EnumMember]
[XmlEnum(Name = "1")]
Monday = 1,
[EnumMember]
[XmlEnum(Name = "2")]
Tuesday = 2,
[EnumMember]
[XmlEnum(Name = "3")]
Wednesday = 3,
[EnumMember]
[XmlEnum(Name = "4")]
Thursday = 4,
[EnumMember]
[XmlEnum(Name = "5")]
Friday = 5,
[EnumMember]
[XmlEnum(Name = "6")]
Saturday = 6,
}