'MigrationSerializer<T>': cannot derive from sealed type 'BsonClassMapSerializer<T>'

'MigrationSerializer<T>.Serialize(BsonSerializationContext, BsonSerializationArgs, T)': no suitable method found to override

'MigrationSerializer<T>.Deserialize(BsonDeserializationContext, BsonDeserializationArgs)': no suitable method found to override

'MigrationSerializer<T>': cannot derive from sealed type 'BsonClassMapSerializer<T>'

'MigrationSerializer<T>.Serialize(BsonSerializationContext, BsonSerializationArgs, T)': no suitable method found to override

'MigrationSerializer<T>.Deserialize(BsonDeserializationContext, BsonDeserializationArgs)': no suitable method found to override

'MigrationSerializer<T>': cannot derive from sealed type 'BsonClassMapSerializer<T>'

'MigrationSerializer<T>.Serialize(BsonSerializationContext, BsonSerializationArgs, T)': no suitable method found to override

'MigrationSerializer<T>.Deserialize(BsonDeserializationContext, BsonDeserializationArgs)': no suitable method found to override

'MigrationSerializer<T>': cannot derive from sealed type 'BsonClassMapSerializer<T>'

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Non-nullable property 'ConnectionString' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'DatabaseName' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Possible null reference return.