How can I save a collection of CultureInfo type using EF Core without adding backing fields?

Question

In a class, I have a collection of type List<CultureInfo> OfficialLanguages. I need to respect domain driven design for this project. I cannot add a backing field of type List<string> officialLanguagesCodes and handle it that way.

When I have a single property like User.Culture, I can handle a conversion like this in my OnModelCreating:

modelBuilder.Entity<User>().Property(u => u.Culture).HasConversion(c => c.Name, s => new(s));

How can I achieve something similar for a collection?

Answer 1

Hi,@Joseph Gregory. Welcome to Microsoft Q&A. 

Use HasConversion to store List<CultureInfo> in the database as a string. You can use the following method.

1.Install Newtonsoft.Json via Nuget

2.Add code

modelBuilder.Entity<User>().Property(e => e.OfficialLanguages).HasConversion(

    v => JsonSerializer.Serialize(v, (JsonSerializerOptions)null),

    v => JsonSerializer.Deserialize<List<CultureInfo>>(v, (JsonSerializerOptions)null));

If the above solutions do not solve your problem, please describe the database and model design more clearly, as well as your expected results. Update:

According to my test, officialLanguage ​​can read it correctly even if you have a private read-only backing field.

If you want officialLanguage to remain private and read-only and the table can correctly insert other fields, you could try adding a default value for officialLanguage.You could refer to the following code.

 

entity.Property(e => e.OfficialLanguages).HasConversion(

    v => JsonSerializer.Serialize(v, (JsonSerializerOptions)null),

    v => JsonSerializer.Deserialize<List<CultureInfo>>(v, (JsonSerializerOptions)null))

    .HasDefaultValue(new List<CultureInfo>() { });

The officialLanguage is set to private read-only. You could only add values ​​to it through the database. You could print out the value to be added as follows and then manually copy it into the database.

//Install Newtonsoft.Json via NuGet

Console.WriteLine(JsonConvert.SerializeObject(new List<CultureInfo>() {

    new CultureInfo() { Id = 1, Name = "AA" },

    new CultureInfo() { Id = 2, Name = "BB" },

    new CultureInfo() { Id = 3, Name = "CC" }

    }));

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