Dictionary to Dictionary

Question

I'm currently working on a .NET Framework 4.7.2 application. Given is a Dictionary<string, object>. I need to write a method to transform the structure to a Dictionary<string, float>.

private List<KeyValuePair<int, Dictionary<string, float>>> CreateResult(List<Dictionary<string, object>> items)
{
    var result = new List<KeyValuePair<int, Dictionary<string, float>>>();

    for (int i = 0; i < items.Count; i++)
    {
       var item = items[i].ToDictionary<string, float>(v => v); // Error, wrong approach
       result.Add(new KeyValuePair<int, Dictionary<string, float>>(i, new Dictionary<string, float>(item)));
    }
    return result;
}

Unfortunately my method does not work, neither I don't really know if it's the right approach to transform all values of my dictionary to type float.

Do you know a good/save way to transform all values in my Dicitonary from type object to type float?

Thank you very much!

https://stackoverflow.com/questions/4942624/how-to-convert-dictionarystring-object-to-dictionarystring-string-in-c-sha — Mitch Wheat, Jan 11 '19 at 12:46
@accordo777 you can write a simple LINQ query to return what you want. Why the KeyValuePair? Do you really need it? — Panagiotis Kanavos, Jan 11 '19 at 13:15
`var result = items.Select(d=>d.ToDictionary(k=>k.Key, k=> Convert.ToSingle(k.Value))).ToList();` — Cihan Yakar, Jan 11 '19 at 13:51

score 2 · Answer 1 · answered Jan 11 '19 at 13:14

You could convert the dictionaries and insert the index with a single (ugly) LINQ statement :

var result=items.Select((dct,i)=>new KeyValuePair<int, Dictionary<string, float>>(
                                           i,
                                           dct.ToDictionary(p=>p.Key,p=>(float)p.Value))
                       ).ToList();

A KeyValuePair doesn't offer any advantages except the property names. You could simplify the query by using value tuples:

var result=items.Select((dct,i)=>(i,dct.ToDictionary(p=>p.Key,p=>(float)p.Value)))
                 .ToList();

And name the tuple items in the return type :

private List<(int index , Dictionary<string, float> dict)> CreateResult(List<Dictionary<string, object>> items)
{
    var result=items.Select((dct,i)=>(i,dct.ToDictionary(p=>p.Key,p=>(float)p.Value)))
                    .ToList();
    return result;
}

score 1 · Answer 2 · answered Jan 11 '19 at 12:47

When you know that the dictionary with object values contains only float values, you can do a typecast in ToDictionary:

private List<KeyValuePair<int, Dictionary<string, float>>> CreateResult(List<Dictionary<string, object>> items)
{
    var result = new List<KeyValuePair<int, Dictionary<string, float>>>();

    for (int i = 0; i < items.Count; i++)
    {
       var item = items[i].ToDictionary<string, float>(v => v.Key, v = (float)v.Value);
       result.Add(new KeyValuePair<int, Dictionary<string, float>>(i, item));
    }
    return result;
}

You can replace the typecast with any conversion that you deem necessary. The important thing is that the return type of the second lambda expression in ToDictionary is float.

NaDeR Star · Accepted Answer · 2019-01-11T13:06:16.880

1

Try this

private List<KeyValuePair<int, Dictionary<string, float>>> CreateResult(List<Dictionary<string, object>> items)
    {
        var result = new List<KeyValuePair<int, Dictionary<string, float>>>();

        for (int i = 0; i < items.Count; i++)
        {
            var currentDic = new Dictionary<string, float>();
            var item = items[i];
            foreach (var itm in item)
            {
                currentDic.Add(itm.Key, (float)itm.Value);
            }

            result.Add(new KeyValuePair<int, Dictionary<string, float>>(i, currentDic));
        }
        return result;
    }

edited Jan 11 '19 at 13:06

answered Jan 11 '19 at 12:55

NaDeR Star

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You've changed the return type, without knowing why OP has used the original return type. – ColinM Jan 11 '19 at 12:57
he said I'm currently working on a .NET Framework 4.7.2 application. Given is a Dictionary. I need to write a method to transform the structure to a Dictionary... – NaDeR Star Jan 11 '19 at 12:59
@NaDeRStar you've changed the result. The OP's code retutns the *index* of each Dictionary as well – Panagiotis Kanavos Jan 11 '19 at 13:00
1

Right with you guys, answer just updated – NaDeR Star Jan 11 '19 at 13:06
thanks for your help! – accordo777 Jan 11 '19 at 13:12

Dictionary to Dictionary

3 Answers3