Copy key values from NameValueCollection to Generic Dictionary

Question

Trying to copy values from an existing NameValueCollection object to a Dictionary. I have the following code below to do that but seems the Add does not accept that my keys and values are as Strings

IDictionary<TKey, TValue> dict = new Dictionary<TKey, TValue>();
public void copyFromNameValueCollection (NameValueCollection a)
{
    foreach (var k in a.AllKeys)
    { 
        dict.Add(k, a[k]);
    }  
}

Note: NameValueCollection contains String keys and values and so I simply want to provide here a method to allow copying of those to a generic dictionary.

Answer 1

It doesn't make sense to use generics here since you can't assign strings to some arbitrary generic type:

IDictionary<string, string> dict = new Dictionary<string, string>();

public void copyFrom(NameValueCollection a)
{
            foreach (var k in a.AllKeys)
            { 
                dict.Add(k, a[k]);
            }  
}

although you should probably create a method to create a new dictionary instead:

public static IDictionary<string, string> ToDictionary(this NameValueCollection col)
{
    IDictionary<string, string> dict = new Dictionary<string, string>();
    foreach (var k in col.AllKeys)
    { 
        dict.Add(k, col[k]);
    }  
    return dict;
}

which you can use like:

NameValueCollection nvc = //
var dictionary = nvc.ToDictionary();

If you want a general way of converting the strings in the collection into the required key/value types, you can use type converters:

public static Dictionary<TKey, TValue> ToDictionary<TKey, TValue>(this NameValueCollection col)
{
    var dict = new Dictionary<TKey, TValue>();
    var keyConverter = TypeDescriptor.GetConverter(typeof(TKey));
    var valueConverter = TypeDescriptor.GetConverter(typeof(TValue));

    foreach(string name in col)
    {
        TKey key = (TKey)keyConverter.ConvertFromString(name);
        TValue value = (TValue)valueConverter.ConvertFromString(col[name]);
        dict.Add(key, value);
    }

    return dict;
}