Why are manually added items to C# dictionary added to beginning/end of dictionary?

Question

Using Oxyplot in my dictionary, I want my user to have the option to choose colors. To fill the corresponding combobox with all Oxycolors I have the following function:

    ...
    public Dictionary<string, OxyColor> AllOxyColors { get; set; }
    ...

    /// <summary>
    /// Creates a Dictionary from the fields of the OxyColorsclass
    /// </summary>
    private void InitializeAllOxyColors()
    {
        var colorsValues = typeof(OxyColors)
         .GetFields(BindingFlags.Static | BindingFlags.Public)
         .Where(f => f.FieldType == typeof(OxyColor))
         .Select(f => f.GetValue(null))
         .Cast<OxyColor>()
         .ToList();

        var colorsNames = typeof(OxyColors)
         .GetFields(BindingFlags.Static | BindingFlags.Public)
         .Where(f => f.FieldType == typeof(OxyColor))
         .Select(f => f.Name)
         .Cast<string>()
         .ToList();

        AllOxyColors = colorsNames.Zip(colorsValues, (k, v) => new { k, v }).ToDictionary(x => x.k, x => x.v);
        AllOxyColors.Remove("Undefined");
        AllOxyColors.Remove("Automatic");
        // Manually added colors for colorblind colleagues
        AllOxyColors.Add("#DE1C1C", OxyColor.Parse("#DE1C1C"));
        AllOxyColors.Add("#13EC16", OxyColor.Parse("#13EC16"));
        AllOxyColors.Add("#038BFF", OxyColor.Parse("#038BFF"));
        // ordering doesn't seem do anything on the dictionary here:
        //AllOxyColors.OrderBy(c => c.Key);
    }

As you can see there is a section where I manually add three colors, that where requested by color blind colleagues. The problem is, that for some reason, the first two colors are added to the top of the list, the third color is added at the end of the list. Using OrderBy() also doesn't seem to have any effect on the dictionary.

What is the reason for this behavior?

Does this answer your question? [The order of elements in Dictionary](https://stackoverflow.com/questions/4007782/the-order-of-elements-in-dictionary) . TLDR: the elements are not stored in any particular order internally. The sequence in which you added them into the dictionary is irrelevant. You can use an OrderedDictionary or SortedDictionary if you need that kind of functionality. — ADyson, Nov 15 '19 at 10:07
@ADyson it seems like it does, will test with ordered dictionary and report back — Roland Deschain, Nov 15 '19 at 10:10
Actually from a bit of brief googling it might be that SortedDictionary is closer to what you need. You might need to try both of them out. — ADyson, Nov 15 '19 at 10:13

score 1 · Accepted Answer · answered Nov 15 '19 at 10:10

1

OrderBy returns IOrderedEnumerable<TSource> it won't sort your existing dictionary, so you have to do something like

AllOxyColors = AllOxyColors.OrderBy(x => x.Key).ToDictionary(pair => pair.Key, pair => pair.Value);

answered Nov 15 '19 at 10:10

Mihir Dave

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Works! Thanks, maybe expand your answer with the info from @ADyson? – Roland Deschain Nov 15 '19 at 10:13
This will work but it strikes me as a bit inefficient to duplicate the entire data structure. – ADyson Nov 15 '19 at 10:14
That is why I asked to add your information to the answer. This is surely not as efficient, but good enough for short data sets I guess? – Roland Deschain Nov 15 '19 at 10:15
Furthermore, atm I can't find a way to .zip() to a `SortedDictionary`, so in my case this seems to be a good solution. – Roland Deschain Nov 15 '19 at 10:20
Yes, I agree @ADyson, I just wanted to give an example of how you can achieve it using the dictionary, but I'll update my answer. – Mihir Dave Nov 15 '19 at 10:21

Why are manually added items to C# dictionary added to beginning/end of dictionary?

1 Answers1