zafeiris.m zafeiris.m - 12 days ago 5
C# Question

Keep casing when serializing dictionaries

I have a Web Api project being configured like this:

config.Formatters.JsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();


However, I want dictionary keys casing to remain unchanged. is there any attribute in
Newtonsoft.Json
I can use to a class to denote that I want casing to remain unchanged during serialization?

public class SomeViewModel
{
public Dictionary<string, string> Data { get; set; }
}

Answer

There is not an attribute to do this, but you can do it by customizing the resolver.

I see that you are already using a CamelCasePropertyNamesContractResolver. If you derive a new resolver class from that and override the CreateDictionaryContract() method, you can provide a substitute DictionaryKeyResolver function that does not change the key names.

Here is the code you would need:

class CamelCaseExceptDictionaryKeysResolver : CamelCasePropertyNamesContractResolver
{
    protected override JsonDictionaryContract CreateDictionaryContract(Type objectType)
    {
        JsonDictionaryContract contract = base.CreateDictionaryContract(objectType);

        contract.DictionaryKeyResolver = propertyName => propertyName;

        return contract;
    }
}

Demo:

class Program
{
    static void Main(string[] args)
    {
        Foo foo = new Foo
        {
            AnIntegerProperty = 42,
            HTMLString = "<html></html>",
            Dictionary = new Dictionary<string, string>
            {
                { "WHIZbang", "1" },
                { "FOO", "2" },
                { "Bar", "3" },
            }
        };

        JsonSerializerSettings settings = new JsonSerializerSettings
        {
            ContractResolver = new CamelCaseExceptDictionaryKeysResolver(),
            Formatting = Formatting.Indented
        };

        string json = JsonConvert.SerializeObject(foo, settings);
        Console.WriteLine(json);
    }
}

class Foo
{
    public int AnIntegerProperty { get; set; }
    public string HTMLString { get; set; }
    public Dictionary<string, string> Dictionary { get; set; }
}

Here is the output from the above. Notice that all of the class property names are camel-cased, but the dictionary keys have retained their original casing.

{
  "anIntegerProperty": 42,
  "htmlString": "<html></html>",
  "dictionary": {
    "WHIZbang": "1",
    "FOO": "2",
    "Bar": "3"
  }
}
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