How to add a property to an EntityType after it has been added to the Data Store?

问题

I have an Entity Framework Code First model with a column that is not mapped which I still want to persist between the server and the client. The model looks similar to this with many more properties:

public class OwnerInformation
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [Required]
    [MaxLength(16)]
    public byte[] SSNEncrypted { get; set; }

    [NotMapped]
    [MaxLength(9)]
    [MinLength(9)]
    public string SSN { get; set; }
}

When the metadata is retrieved by Breeze SSN is not part of it, but when the data is sent over the wire the SSN is there. I would like to let breeze deal with the mapping through the metadata, but I would like to be able to still pass SSN between the client and the server and track it's state as I need to encrypt it before it is saved to the DB.

I tried adding it after the metadata is fetched like this:

var ownerType = manager.metadataStore.getEntityType('OwnerInformation');
var sSN = new breeze.DataProperty({
  name: 'sSN',
  dataType: breeze.DataType.String,
  isNullable: false,
  maxLength: 9
});
ownerType.addProperty(sSN);

but I get the error: The 'OwnerInformation:#Models' EntityType has already been added to a MetadataStore and therefore no additional properties may be added to it.

Maybe I'm overthinking this and there is an easier way. I'm opened to any suggestions.

回答1:

I took a different approach and decided to change the metadata at runtime on the server. Here's how I did it.

public class MyContextProvider : EFContextProvider<MyContext>
{
  protected override string BuildJsonMetadata()
  {
    string metadata = base.BuildJsonMetadata();
    JObject json = JObject.Parse(metadata);
    var entityOwnerInfo = json["schema"]["entityType"].Children().Where(j => (string)j["name"] == "OwnerInformation").SingleOrDefault();
    var propertyArray = entityOwnerInfo["property"] as Newtonsoft.Json.Linq.JArray;

    JToken ssnPropertyType = JToken.Parse(@"{
      ""name"": ""SSN"",
      ""type"": ""Edm.String"",
      ""fixedLength"": ""true"",
      ""maxLength"": ""9"",
      ""minLength"": ""9"",
      ""nullable"": ""false""}");
    propertyArray.Add(ssnPropertyType);

    return json.ToString();
  }
}

回答2:

Actually it's a really good question. Breeze doesn't currently support modifying an EntityType after it has been added to the MetadataStore. But with your scenario I see the use case and I like your workaround.

I will add a feature request that allows this to be done more easily. Not sure yet exactly what this will look like, but... Thanks for the scenario.

来源：https://stackoverflow.com/questions/18118091/how-to-add-a-property-to-an-entitytype-after-it-has-been-added-to-the-data-store

标签

breeze