Entity Framework intermittently set the byte field into 255 - entity-framework

Question

I have a piece of code that inserts into a table. Simply, I have a table with structure
Table1:
Id int PK
Type tinyint
Status tinyint
After digging in our PROD, I observed that EF might be intermittently defaulting the value to 255 when the value should range (1-3). I understand 255 is the max value for tinyint in SQL Server but I have no defaults in both table definition and in EDMX.
Usage:
//OUTAGE_TYPE
public enum OUTAGE_TYPE
{
Unknown = -1,
SwitchingPlan = 1,
PlannedIncident = 2,
UnplannedIncident = 3
}
//CREATE INSTANCE
var outage = new Outage
{
OutageTypeId = (byte)OUTAGE_TYPE.SwitchingPlan,
OutageStatusId = (byte)OUTAGE_STATUS.Approved,
IncidentRID = incident.RID,
WorkRID = incident.WorkRID,
ETR = incident.ETR,
DateInserted = Time.Now(),
DateUpdated = Time.Now()
};
Captured SQL:
INSERT [dbo].[Outage]([OutageTypeId], [OutageStatusId], [IncidentRID], [WorkRID], [ETR], [DateInserted], [DateUpdated])
VALUES (#0, #1, #2, NULL, #3, #4, #5)
SELECT [Id]
FROM [dbo].[Outage]
WHERE ##ROWCOUNT > 0 AND [Id] = scope_identity()
-- #0: '255' (Type = Byte, Size = 1)
-- #1: '1' (Type = Byte, Size = 1)
-- #2: 'INC 11000700' (Type = String, Size = 255)
-- #3: '05-08-2016 10:05:52' (Type = DateTime2)
-- #4: '05-08-2016 22:05:22' (Type = DateTime2)
-- #5: '05-08-2016 22:05:22' (Type = DateTime2)
-- Executing at 06-08-2016 00:06:00 +02:00
Error:
The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Outage_OutageType". The conflict occurred in database "ONSP", table "dbo.OutageType", column 'Id'.
I was not able to reproduce on my local machine, maybe you guys have experienced this before. Many thanks.

Answer 1

After my colleague and me digging around, we found the root cause of this problem.
First -1, is not a valid value for a byte and direct conversion will not throw exception but will yield to byte.MaxValue
void Main()
{
var type = OUTAGE_TYPE.Unknown;
var result = (byte)type;
//result = 255!!!
Console.WriteLine(result);
}
public enum OUTAGE_TYPE
{
Unknown = -1,
SwitchingPlan = 1,
PlannedIncident = 2,
UnplannedIncident = 3
}