ArangoDb.Net upsert always insert - arangodb

Question

I'm making a small application with CRUD functions with ArangoDatabase and its driver:
http://www.arangoclient.net/
Here is my code:
var insert = new Account
{
Email = "email01#gmail.com",
FirstName = "Adam",
LastName = "Smith"
};
var update = new Account
{
Email = "email01#gmail.com",
FirstName = "John",
LastName = "Peterson"
};
using (var arangoDatabase = new ArangoDatabase(new DatabaseSharedSetting()
{
Url = "http://127.0.0.1:8529/",
Database = "_system",
Credential = new NetworkCredential()
{
UserName = "root",
Password = "xvxvc"
}
}))
{
arangoDatabase.Query()
.Upsert(_ => new Account() {Email = insert.Email},
_ => insert, ((aql, x) => update))
.In<Account>()
.Execute();
}
For the first time running, [insert] object is added to database.
Therefore, my database now is :
But at the second time of running code, it throws me an error :
unique constraint violated (while executing). ErrorNumber: 1210 HttpStatusCode: 409
The question is: What is my problem and how to solve it?
Thank you,

Answer 1

Problem could be upsert search expression serialization:
Assume Account class definition is:
public class Account
{
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
upsert search expression: new Account() {Email = insert.Email} will serializes to:
{ Email: "email01#gmail.com", FirstName: null, LastName: null }
but what is expected is:
{ Email: "email01#gmail.com" }
Since search expression will never found a document, then insert will occur and you get unique constraint violated.
There are two solution to avoid serializing FirstName and LastName members:
One is we could use Json.net JsonProperty attribute to ignore nulls in serialization:
public class Account
{
public string Email { get; set; }
[Newtonsoft.Json.JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public string FirstName { get; set; }
[Newtonsoft.Json.JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public string LastName { get; set; }
}
And the other way is to use an anonymous object for search expression:
arangoDatabase.Query()
.Upsert(_ => new Account() {Email = insert.Email}
// should be
arangoDatabase.Query()
.Upsert(_ => new {Email = insert.Email}
One note about using anonymous object is that Email member could resolve to something else base on what you specify for its naming convention, for example:
public class Account
{
[DocumentProperty(Identifier = IdentifierType.Key)]
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
If you specify Email as a Key identifier, then you should use _key in the anonymous object:
arangoDatabase.Query()
.Upsert(_ => new { _key = insert.Email }