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I need to implement a custom functionality a bit similar Dictionary but with the possibility to insert duplicate keys. So basically what I need from Dictionary is the possibility to serialize the object as the following JSON:

{ "One":"Value 1", "Two":"Value x", "One":"Value 10", "Two":"Value 100" }

As you can see above I have duplicate keys ...

Any advice? The whole point is the JSON output in the format above

Edit:

KeyValuePair<string,string> doesn't work!

This is the outcome:

[{"Key":"One","Value":"Two"},{"Key":"One","Value":"Two"}]

As you can see serialized as JSON will brink the Key and Value keywords in place where a Dictionary will replace the Key with the actual key-value and the value with the value provided.

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  • 2
    You don't want a Dictionary. You want List<KeyValuePair<string, string>>(); Commented May 20, 2015 at 15:19
  • 1
    I think it doesn't make sense to have a Dictionary with duplicate keys. Explain better what you wanna do. Commented May 20, 2015 at 15:19
  • That's not a dictionary. What value should returned on MyDict["One"]? Commented May 20, 2015 at 15:20
  • @Galma88: As you can read from the question I want a similar functionality as Dictionary provides but with the possibility to add duplicate keys, I believe is obvious I know that Dictionary doesn't support duplicate keys, right? Commented May 20, 2015 at 15:24
  • A list of KeyValuePair is the best approach. Commented May 20, 2015 at 15:27

4 Answers 4

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You can use a List<KeyValuePair<TKey, TValue>> instead of a Dictionary<TKey, TValue>. In your case, it would be a List<KeyValuePair<string, string>>.

Edit:

If you're using Json.NET for serialization of the JSON, you can achieve your desired output using a custom converter. The answer here provides it (I made slight modifications):

class KeyValuePairConverter : JsonConverter { public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { var list = value as List<KeyValuePair<string, string>>; writer.WriteStartArray(); foreach (var item in list) { writer.WriteStartObject(); writer.WritePropertyName(item.Key); writer.WriteValue(item.Value); writer.WriteEndObject(); } writer.WriteEndArray(); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { // TODO... } public override bool CanConvert(Type objectType) { return objectType == typeof(List<KeyValuePair<string, string>>); } }
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2 Comments

KeyValuePair will output Key and Value within the JSON but Dictionary will provide the actual values as Key and value ... I made an edit to my question.
@YuvalItzchakov please see related post: stackoverflow.com/questions/39583463/…
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You may want to use List<Tuple<string,string>>

 List<Tuple<string, string>> values = new List<Tuple<string, string>>(); values.Add(new Tuple<string, string>("One", "Value 1")); values.Add(new Tuple<string, string>("Two", "Value x")); values.Add(new Tuple<string, string>("One", "Value 10"));

EDIT: If the property names are important, why not simply try something like: List<MyClass>

class MyClass { public string Key { get; set; } public string Value { get; set; } }
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Tuple doesn't work either, because will output Item1, Item2, etc etc. please check the JSON example I provided in the question.
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Use an array of a custom class.

MyClass[] array; public class MyClass { public string Key { get; set; } public string Value { get; set; } }
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You could do something like this (knocked it up quickly in console) but shoudl be enough to get the idea...

using System.IO; using System; using System.Text; using System.Collections.Generic; class Program { static void Main() { List<Tuple<string, string>> values = new List<Tuple<string, string>>(); values.Add(new Tuple<string, string>("One", "Value 1")); values.Add(new Tuple<string, string>("Two", "Value x")); values.Add(new Tuple<string, string>("One", "Value 10")); Console.Write(Format.ToJson(values)); } } static class Format { public static string ToJson(List<Tuple<string, string>> values) { StringBuilder builder = new StringBuilder(); foreach(var item in values) { builder.Append(string.Format("{{{0}:{1}}},", item.Item1, item.Item2)); } return "{" + builder.ToString() + "}"; } }
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ToJson, is that valid Json format? What if I want a format like [{{}.{},{}}, {{},{},{}},...}] like that?

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