Getting an Enum to display on client side - asp.net-web-api

Question

I'm having hard time understanding how to convert an Enum value to it's corresponding name. My model is as follows:
public class CatalogRule
{
public int ID { get; set; }
[Display(Name = "Catalog"), Required]
public int CatalogID { get; set; }
[Display(Name = "Item Rule"), Required]
public ItemType ItemRule { get; set; }
public string Items { get; set; }
[Display(Name = "Price Rule"), Required]
public PriceType PriceRule { get; set; }
[Display(Name = "Value"), Column(TypeName = "MONEY")]
public decimal PriceValue { get; set; }
[Display(Name = "Exclusive?")]
public bool Exclude { get; set; }
}
public enum ItemType
{
Catalog,
Category,
Group,
Item
}
public enum PriceType
{
Catalog,
Price_A,
Price_B,
Price_C
}
A sample result from .net API:
[
{
$id: "1",
$type: "XYZ.CMgr.Models.CatalogRule, XYZ.CMgr",
ID: 1,
CatalogID: 501981,
ItemRule: 0,
Items: "198",
PriceRule: 1,
PriceValue: 0.5,
Exclude: false
},
{
$id: "2",
$type: "XYZ.CMgr.Models.CatalogRule, XYZ.CMgr",
ID: 2,
CatalogID: 501981,
ItemRule: 2,
Items: "9899",
PriceRule: 2,
PriceValue: 10.45,
Exclude: false
}
]
So in this example, I need to get Catalog for results[0].ItemRule & Price A for results[0].PriceRule. How can I accomplish this in BreezeJS??

Answer 1

This is easy to do in ASP.NET Web API, because it is an out-of-box feature in the default JSON serializer (Json.NET).
To see strings instead of enum numbers in JSON, just add an instance of StringEnumConverter to JSON serializer settings during app init:
var jsonFormatter = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
jsonFormatter.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
UPDATE: Yep, you right, this is not help with Breeze.js. Ok, you can anyway do a little magic to make enums work like strings (while new version with fix is not released).
Create a custom ContextProvider which updates all integer enum values in metadata to strings. Here it is:
public class StringEnumEFContextProvider<T> : EFContextProvider<T>
where T : class, new()
{
protected override string BuildJsonMetadata()
{
XDocument xDoc;
if (Context is DbContext)
{
xDoc = GetCsdlFromDbContext(Context);
}
else
{
xDoc = GetCsdlFromObjectContext(Context);
}
var schemaNs = "http://schemas.microsoft.com/ado/2009/11/edm";
foreach (var enumType in xDoc.Descendants(XName.Get("EnumType", schemaNs)))
{
foreach (var member in enumType.Elements(XName.Get("Member", schemaNs)))
{
member.Attribute("Value").Value = member.Attribute("Name").Value;
}
}
return CsdlToJson(xDoc);
}
}
And use it instead of EFContextProvider in your Web API controllers:
private EFContextProvider<BreezeSampleContext> _contextProvider =
new StringEnumEFContextProvider<BreezeSampleContext>();
This works well for me with current Breeze.js version (1.1.3), although I haven't checked other scenarios, like validation...
UPDATE: To fix validation, change data type for enums in breeze.[min|debug].js, manually (DataType.fromEdmDataType function, dt = DataType.String; for enum) or replace default function during app init:
breeze.DataType.fromEdmDataType = function (typeName) {
var dt = null;
var parts = typeName.split(".");
if (parts.length > 1) {
var simpleName = parts[1];
if (simpleName === "image") {
// hack
dt = DataType.Byte;
} else if (parts.length == 2) {
dt = DataType.fromName(simpleName);
if (!dt) {
if (simpleName === "DateTimeOffset") {
dt = DataType.DateTime;
} else {
dt = DataType.Undefined;
}
}
} else {
// enum
dt = DataType.String; // THIS IS A FIX!
}
}
return dt;
};
Dirty, dirty hacks, I know... But that's the solution I found

Answer 2

There will be a new release out in the next few days where we "change" breeze's enum behavior ( i.e. break existing code with regards to enums). In the new release enums are serialized and queried by their .NET names instead of as integers. I will post back here when the new release is out.