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c#linqdictionary
Matias Cicero
Matias Cicero

Reputation: 26311

LINQ operations on IDictionary

Let's suppose I have the following dictionaries:

private Dictionary<int, string> dic1 = new Dictionary<int, string>()
{
      { 1, "a" },
      { 2, "b" },
      { 3, "c" }
}

private Dictionary<SomeEnum, bool> dic2 = new Dictionary<SomeEnum, bool>()
{
      { SomeEnum.First, true },
      { SomeEnum.Second, false },
      { SomeEnum.Third, false }
}

I want to convert these two dictionaries into a Dictionary<string, object>

For example:

 dic1 = new Dictionary<string, object>()
 {
     { "1", "a" },
     { "2", "b" },
     { "3", "c" }
 }

 dic2 = new Dictionary<string, object>()
 {
     { "First", true },
     { "Second", false },
     { "Third", false }
 }

As you can see, the string key of these dictionaries is just the string representation of the previous ones.

The method that is responsible for the conversion has the following signature:

 public static object MapToValidType(Type type, object value)
 {
     //....

     if(typeof(IDictionary).IsAssignableFrom(type))
     {
         //I have to return a Dictionary<string, object> here
         return ??;
     }
 }

I have tried the following:

 ((IDictionary)value).Cast<object>().ToDictionary(i => ...);

But i was casted to an object, so I cannot access the key or value items. For that I would need to cast it to the appropiate KeyValuePair<TKey, TValue>, but I don't know TKey or TValue type.

Another solution is to do this:

IDictionary dic = (IDictionary)value;
IList<string> keys = dic.Keys.Cast<object>().Select(k => Convert.ToString(k)).ToList();
IList<object> values = dic.Values.Cast<object>().ToList();
Dictionary<string, object> newDic = new Dictionary<string, object>();
for(int i = 0; i < keys.Count; i++)
   newDic.Add(keys[0], values[0]);
return newDic;

However, I'm not much of a fan of this approach and I am really looking for a simpler and friendlier one line LINQ statement.

Upvotes: 11

Views: 6961

Answers (4)

Kevin
Kevin

Reputation: 2291

The trick is to cast your IDictionary to a generic type of DictionaryEntry. Then you can use ToDictionary() from System.Linq. 

static Dictionary<string,object> ToDictionary(IDictionary dic)
{
    return dic.Cast<DictionaryEntry> ().ToDictionary ((t) => t.Key.ToString (), (t) => t.Value);
}

Upvotes: 2

BhavO
BhavO

Reputation: 2399

public static IDictionary<string, object> Convert<TKey, TValue>(IDictionary<TKey, TValue> genDictionary)
{
    return genDictionary.Select(kvp => new KeyValuePair<string, object>(kvp.Key.ToString(), (object)kvp.Value)).ToDictionary(x => x.Key, x => x.Value);
}

called like:

    var dicIntInt = new Dictionary<int, string>{{123, "asdc"}, {456, "aa"} };

    Dictionary<string, object> dicStrObj = Convert(dicIntInt);

https://dotnetfiddle.net/eY41MQ

Upvotes: 0

Jared Moore
Jared Moore

Reputation: 3805

    static void Main(string[] args)
    {
        var blah = KeyToString(dic1);

        // Verify that we converted correctly
        foreach (var kvp in blah)
        {
            Console.WriteLine("{0} {1}, {2} {3}", kvp.Key.GetType(), kvp.Key, kvp.Value.GetType(), kvp.Value);
        }
    }

    static Dictionary<string, TValue> KeyToString<TKey, TValue>(IEnumerable<KeyValuePair<TKey, TValue>> dic1)
    {
        return dic1.ToDictionary(kvp => kvp.Key.ToString(), kvp => kvp.Value);
    }

Upvotes: 1

George
George

Reputation: 787

You can try this, no LINQ though, i think you don't need:

 Dictionary<string, object> ConvertToDictionary(System.Collections.IDictionary iDic) {
            var dic = new Dictionary<string, object>();
            var enumerator = iDic.GetEnumerator();
            while (enumerator.MoveNext()) {
                dic[enumerator.Key.ToString()] = enumerator.Value;
            }
        return dic;
    }

Or a Linq one:

return iDic.Keys.Cast<object>().ToDictionary(k=> k.ToString(), v=> iDic[v]);

Upvotes: 7

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