Can I use dot notation for accessing dictionary values?

Question

I'm using Dictionary<string, string> as configuration for instruments, and it'd be easier for my users who don't know a lot about programming to be able to get autocomplete from Visual Studio.

In Python I can make a Dictionary and access the different values with a dot operator.

d = {'name':'Joe', 'mood':'grumpy'}
d.name
d.mood

Does C# have a way to do this?

I realize all of the problems involved since dictionary is a just a generic collection (how generic? is it just a list of KeyValuePairs? interesting question). I'm not about to write a wrapper class for this to accomplish it (I'd like it to be a bit more flexible than using explicit properties with a custom class).

score 7 · Accepted Answer · edited Jul 13 '20 at 09:05

7

You can already do that in C# with anonymous types:

var d = new { name = "Joe", mood = "grumpy"};
d.name
d.mood

Or real types:

var d = new Person { Name = "Joe", Mood = "grumpy"};
d.Name
d.Mood

And, in C# 4.0 we will have the DLR which will allow adding properties at runtime using the ExpandoObject:

dynamic d = new ExpandoObject();
d.name = "Joe";
d.mood = "grumpy";

However, I'm not sure that you can do IntelliSense using static analysis in C#.

The closest C# equivalent to what you have is

var d = new Dictionary<string, string>()
    { { "name", "Joe" }, { "mood", "grumpy" } };
d["name"]
d["mood"]

Which will not support IntelliSense.

If you are making an API, I would use real types.

edited Jul 13 '20 at 09:05

workerbee

57
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answered Feb 08 '10 at 16:45

John Gietzen

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`dynamic` won't let you add properties at run time by itself. `ExpandoObject` does all the magic, and you have to initialize that instead of an anonymous type. – Blindy Feb 08 '10 at 16:48
awesome. I didn't know about that. the whole api situation is a bit silly, but this is the easiest way I can keep people out of trouble, which is really what matters at the end of the day – Oren Mazor Feb 08 '10 at 17:12
Keep in mind that if you are relying on the users to create anonymous types, you will need to use reflection or the "dynamic" keyword to access the values. – John Gietzen Feb 08 '10 at 17:14

score 0 · Answer 2 · answered Feb 08 '10 at 16:43

0

Seems like you want a struct. http://msdn.microsoft.com/en-us/library/0taef578.aspx

Edit: changed to a more up-to-date link.

answered Feb 08 '10 at 16:43

Alison R.

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I rather like the idea of using a struct, provided you know what the fields/properties should be in advance. Which presumably you would if you're documenting it. – Powerlord Feb 08 '10 at 16:56

score 0 · Answer 3 · edited May 23 '17 at 10:34

you are looking for imo method chaining.

Method chaining - why is it a good practice, or not?

a dictionary object is a collection (uses list) of key value pairs that also implements a hash table for access. It is almost n(1) in terms of its access speed.

public class Dictionary<TKey, TValue> : IDictionary<TKey, TValue>, 
    ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, 
    IDictionary, ICollection, IEnumerable, ISerializable, IDeserializationCallback

taken from

ms-help://MS.VSCC.v90/MS.MSDNQTR.v90.en/fxref_mscorlib/html/589059d3-d7f8-e09b-705d-91a461971cc2.htm

In fact the retrieval algorithm changes as it gets larger as a hash table is less efficient for small numbers of items.

The linq approach would work also - no need to use anonymous types though

moodyPerson p = new moodyPerson{mood = "good", name="jim"};

however this does not force you to set all the properties of a moody person and will use its empty constructor.

you cant use intellisense if you want to access properties by strings. You would need to use reflection to implement this.

Looking at the source code for Dictionary https://referencesource.microsoft.com/#mscorlib/system/collections/generic/dictionary.cs,297 I cant see that the alg changes with the size — Magnus, Jul 13 '20 at 09:34

score 0 · Answer 4 · answered May 24 '17 at 18:22

Don't get suckered into an elaborate solution with ExpandoObject() if you are planning to instantiate your objects at runtime (like from a database call), there is no intellisense for "dot notation"and it will produce a compile error if you try to use it. you can use ["propname"] bracket notation to access them however at this point you might as well have created custom class objects or just manipulate the values as needed in a DataTable()

Can I use dot notation for accessing dictionary values?

4 Answers4