Michael Freidgeim 7:34 am on June 3, 2011  

JavaScriptSerializer extension DeserializeDictionary

When Iā€™ve tried to deserialize dictionary whis strongly typed(and not string) keys, Iā€™ve got an exception similar to the following

Type ā€˜System.Collections.Generic.Dictionary`2[[System.Drawing.KnownColor, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a],[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]ā€™ is not supported for serialization/deserialization of a dictionary, keys must be strings or objects.
// Type Dictionary`2 is not supported for serialization/deserialization of a dictionary, keys must be strings or objects.

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To workaround the limitation, Iā€™ve created an extension, similar to what was used for serialization inĀ 

http://dukelupus.wordpress.com/2011/05/04/asp-net-mvc-json-and-a-generic-dictionary/

static class DictionaryExtensions
{
public static Dictionary<TKey, TValue>  DeserializeDictionary<TKey, TValue>(this JavaScriptSerializer jss, string jsonText)
{
    var dictWithStringKey = jss.Deserialize<Dictionary<string,TValue>>(jsonText);
    var dict=dictWithStringKey.ToDictionary(de => jss.ConvertToType<TKey>(de.Key),de => de.Value);
        return dict;
}
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///
///From //http://dukelupus.wordpress.com/2011/05/04/asp-net-mvc-json-and-a-generic-dictionary/
///
public static Dictionary<string, object> ToJsonDictionary<TKey, TValue>(this Dictionary<TKey, TValue> input)
{
    var output = new Dictionary<string, object>(input.Count);
    foreach (KeyValuePair<TKey, TValue> pair in input)
        output.Add(pair.Key.ToString(), pair.Value);
    return output;
}
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}

The example code to test is the following.

Note that you can use single quotes in json data, declared within a string. In this case you will not needĀ  to escape double-quotes(ā€œ)

using System.Web.Script.Serialization;
using System.Drawing;//http://msdn.microsoft.com/en-us/library/system.drawing.knowncolor.aspx
void Main()
{
    //http://procbits.com/2011/04/21/quick-json-serializationdeserialization-in-c/
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    string jsonText=@"{        'Yellow':2,        'Green': 1,        'Red': 3}    ";         
        var jss = new JavaScriptSerializer();
        var dictEnum = jss.DeserializeDictionary<KnownColor,int>(jsonText);
    Console.WriteLine(jss.Serialize(dictEnum.ToJsonDictionary()));
    Console.WriteLine(dictEnum[KnownColor.Yellow]);
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}

Ā Related links:

Json.NET (thanks to Guilherme Cardoso )

JSON Serializers In .NET

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MSDN Stand-Alone JSON Serialization

The ASP.NET AJAX Serialization Process ā€“ CodeProject
MSDN DeserializeObject
MSDN JavaScriptSerializer.ConvertToType<T> Method (Object)
MSDN JavaScriptConverter
MSDN SimpleTypeResolver Class (System.Web.Script.Serialization)
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