如果我创建了一个隐式类型转换运算符，我可以让Raven DB序列化一个对象，因为它会成为一个字符串吗？

Question

I have a class that looks something like this:

public class MyClass
{
    string _value;

    public static implicit operator MyClass (string value)
    {
        return new MyClass(value);
    }

    MyClass(string value)
    {
        // Do something...
        _value = value;
    }

    public override string ToString()
    {
         // Do something...
         return _value;
    }
}

Hence, I can use the class like this:

MyClass a = "Hello!";

But in Raven DB it will just be stored like

"SomeProperty": {}

since it has no public properties. And it is quite useless.

To solve this I would make the _value private member a public property instead, like this:

public string Value { get; set; }

and Raven DB will store

"SomeProperty": { "Value": "Hello!" }

and it will be deserializable.

But I don't want this public property. Can I somehow make Raven DB serialize and deserialize the class as was it would a string? Like:

"SomeProperty": "Hello!"

Answer 1

Hi I know this is old but I thought I would add some additions to Ayendes' reply to help people who like me had the same issue and spent hours looking on forums for an answer (of which there were a few but none had any example that you could follow), it's not hard to figure this out but with an example I could have solved this in 10 minutes as opposed to spending a few hours.

My problems was that we have custom value type structs in our application the example I will use is EmailAddress. Unfortunately in Ravendb we could not run queries against these types without defining a custom serialiser.

Our Value Type looked Like this:

[DataContract(Namespace = DataContractNamespaces.ValueTypes)]
public struct EmailAddress : IEquatable<EmailAddress>
{
    private const char At = '@';

    public EmailAddress(string value) : this()
    {
        if (value == null)
        {
            throw new ArgumentNullException("value");
        }

        this.Value = value;
    }

    public bool IsWellFormed
    {
        get
        {
            return Regex.IsMatch(this.Value, @"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*");
        }
    }

    public string Domain
    {
        get
        {
            return this.Value.Split(At)[1];
        }
    }

    [DataMember(Name = "Value")]
    private string Value { get; set; }

    public static bool operator ==(EmailAddress left, EmailAddress right)
    {
        return left.Equals(right);
    }

    public static bool operator !=(EmailAddress left, EmailAddress right)
    {
        return !left.Equals(right);
    }

    public override bool Equals(object obj)
    {
        if (obj == null)
        {
            return false;
        }

        return this.Equals(new EmailAddress(obj.ToString()));
    }

    public override int GetHashCode()
    {
        return this.Value.GetHashCode();
    }

    public override string ToString()
    {
        return this.Value;
    }

    public bool Equals(EmailAddress other)
    {
        return other != null && this.Value.Equals(other.ToString(), StringComparison.OrdinalIgnoreCase);
    }
}

The type of document we wanted to save and query would look something like this

public class Customer
{
    public Guid Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public EmailAddress Email { get; set; }
}

The custom serialiser to store our email as a raw string and then convert it back to its value type on retrieval looked like this:

public class EmailConverterTest : JsonConverter
{

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(EmailAddress);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        EmailAddress actualAddress =  new EmailAddress(reader.Value.ToString());

        return actualAddress;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        EmailAddress actualAddress = (EmailAddress)value;
        string stringEmail = actualAddress.ToString();
        writer.WriteValue(stringEmail);
    }
}

Finally I wired it up and was able to query everything as follows:

    public static void serializercustom(Newtonsoft.Json.JsonSerializer serialiser)
    {
        serialiser.Converters.Add(new EmailConverterTest());
    }

    public static void TestCustomer()
    {
        using (var documentStore = new DefaultDocumentStore())
        {
            documentStore.ConnectionStringName = Properties.Settings.Default.SandBoxConnection;
            documentStore.Initialize();
            documentStore.Conventions.CustomizeJsonSerializer = new Action<Newtonsoft.Json.JsonSerializer>(serializercustom);

            var customer = new Customer
            {
                Id = Guid.NewGuid(),
                FirstName = "TestFirstName",
                LastName = "TestLastName",
                Email = new EmailAddress("testemail@gmail.com")
            };

            // Save and retrieve the data
            using (var session = documentStore.OpenSession())
            {
                session.Store(customer);
                session.SaveChanges();
            }

            using (var session = documentStore.OpenSession())
            {
                var addressToQuery = customer.Email;
                var result = session.Query<Customer>(typeof(CustomerEmailIndex).Name).Customize(p => p.WaitForNonStaleResults()).Where(p => p.Email == addressToQuery);

                Console.WriteLine("Number of Results {0}", result.Count()); // This always seems to return the matching document
            }
        }
    } 

Answer 2

You can write a JsonConverter and teach RavenDB how you want to store the data. After you write the converter, register it in the store.Conventions.CustomizeSerializer event.