# MongoDB, C# and DateTimeOffset


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The [MongoDB driver for C#/.NET](https://docs.mongodb.com/ecosystem/drivers/csharp/)  can currently be serialized/deserialized in three different ways - as an array, object or string.
 
You can control the BSON representation of your property by adding the `[BsonRepresentation]` attribute or set it on your class map.

```csharp
[BsonRepresentation(BsonType.String)]
public DateTimeOffset EventStart { get; set; }
```
 
As mentioned the [DateTimeOffsetSerializer](https://github.com/mongodb/mongo-csharp-driver/blob/master/src/MongoDB.Bson/Serialization/Serializers/DateTimeOffsetSerializer.cs) supports three different representation types:
 
- `BsonType.Array` (default)
- `BsonType.Document`
- `BsonType.String`

## Array representation (default)
 
By default `DateTimeOffset` is serialized as an array consisting of the ticks and the offset in minutes.

```csharp
// Serialization code for BsonType.Array
bsonWriter.WriteStartArray();
bsonWriter.WriteInt64(value.Ticks);
bsonWriter.WriteInt32((int)value.Offset.TotalMinutes);
bsonWriter.WriteEndArray();

// Example JSON output
// [NumberLong("636415154304356493"), 120]
```
 
This is probably the reason you are here right now. This is different than `DateTime` which is stored as a BSON date (`ISODate("2017-09-20T12:46:53.552Z")`) and it makes it harder to query manually and harder to read.
 
I'm sure there's a good reason why this was made the default, but I'm not exactly sure why.
 
## String representation
 
The string representation is more recognizable to most people and probably what you are looking for.

```csharp
// Serialization code for BsonType.String
bsonWriter.WriteString(JsonConvert.ToString(value));

// Example JSON output
// "2017-09-20T14:47:37.8324739+02:00"
```
 
## Document representation
 
The last of the three options is the document representation, which is more or less a combination of the array and string representation combined in an object (document).

```csharp
// Serialization code for BsonType.Document
bsonWriter.WriteStartDocument();
bsonWriter.WriteDateTime("DateTime", BsonUtils.ToMillisecondsSinceEpoch(value.UtcDateTime));
bsonWriter.WriteInt64("Ticks", value.Ticks);
bsonWriter.WriteInt32("Offset", (int)value.Offset.TotalMinutes);
bsonWriter.WriteEndDocument();

// Example JSON output
// {
//     "DateTime": ISODate("2017-09-20T12:56:06.642Z"),
//     "Ticks": NumberLong("636415161666429142"),
//     "Offset": 120
// }
```
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