Enum type can have only integral values (int, short, etc) and string values can not be used in enum...
See if using const will help you..
public struct LogTypes
{
public const string ModifiedUser = "ee538d12-1de4-4a6f-a3dc-32840ea530e0";
public const string ModifiedTicket = "fde92cb8-3d4f-4988-b80e-70701e5efeea";
public const string FailedToLogin = "ffc876ef-4177-4706-8fed-4f2d104769ba";
}
With this you can use like LogTypes.ModifiedUser.