c# nested dictionarys

Hello i have an issue which is similar to this:

http://stackoverflow.com/questions/13334677/creating-three-level-nested-dictionary-in-c-sharp

the comment:
"... and so on. It can be a bit cumbersome to write, so if you need it a lot, I suggest you create an extension method on dictionary that lets you do this easily."

How can i create this extension methode i dont want to create the key everytime.

Please can someone provide me with a full code snippet?

 

I can't really write it for you without knowing what you need (and to be honest, I usually don't write code for others anyway) but this should hopefully get you on the right path:
https://unity3d.com/learn/tutorials/topics/scripting/extension-methods

Calling an Extension Method (SomeClass.cs)

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SomeClass : MonoBehaviour
5. {
6.     void Start () {
7.         //Notice how you pass no parameter into this
8.         //extension method even though you had one in the
9.         //method declaration. The transform object that
10.         //this method is called from automatically gets
11.         //passed in as the first parameter.
12.         transform.ResetTransformation();
13.     }
14. }

Creating an Extension Method (ExtensionMethod.cs)

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. //It is common to create a class to contain all of your
5. //extension methods. This class must be static.
6. public static class ExtensionMethods
7. {
8.     //Even though they are used like normal methods, extension
9.     //methods must be declared static. Notice that the first
10.     //parameter has the 'this' keyword followed by a Transform
11.     //variable. This variable denotes which class the extension
12.     //method becomes a part of.
13.     public static void ResetTransformation(this Transform trans)
14.     {
15.         trans.position = Vector3.zero;
16.         trans.localRotation = Quaternion.identity;
17.         trans.localScale = new Vector3(1, 1, 1);
18.     }
19. }

The trick is to pay attention to the part (this Transform trans). That is what makes it available to Transforms (and the .transform reference by extended extension).

 

Hello this is a c# question: i want to do:


mydictionary[key1][key2][key3] = something

right now i have to add two lines more which i want to avoid somehow:

mydictionary.Add(key1, new something)

mydictionary[key1].Add(key2, new something)

mydictionary[key1][key2][key3] = something

 

That is covered in the original link

Code (CSharp):

1. var data = new Dictionary<string, new Dictionary<string, new Dictionary<string, int>>>();
2.  
3. data["bob"]["jim"]["mark"] = 20;
4. Debug.Log(name+"::Dictionary result: "+ data["bob"]["jim"]["mark"];

Or create an extension method for Dictionary to do that first line for you as a custom type.

 

i have right now a construction like this i did use it quite extensive already and don't want to have to edit my file too much::


public class d1 : Dictionary<string, string> {
}
public class d2 : Dictionary<string, d1> {
}
public class d3 : Dictionary<string, d2> {
}

I know it should be pretty easy but i am just not savy enough with classes /custom types to figure out how.

 

I would strongly advise the adaption of your code to create and access the nested dictionaries to the way it is done in Kerm_Ed's post.

Since you are storing strings, in your case the code would look like this:

Code (csharp):

1.  
2. // Nested dictionary instantiation
3. Dictionary mydictionary = new Dictionary<string, new Dictionary<string, new Dictionary<string, string>>>();
4.  
5. // Nested dictionary access
6. string key1;
7. string key2;
8. string key3;
9. string newValue;
10.  
11. mydictionary[key1][key2][key3] = newValue;

 

Code (CSharp):

1. public Dictionary<string,  Dictionary<string,  Dictionary<string, string>>> globaldict = new Dictionary<string, new  Dictionary<string, new  Dictionary<string, string>>>();

The Line gives me syntax errors "> expected" on the second and third "new". I dont think it can be done this way.

 

Can someone please tell me why and how to work around this problem.

 

You can't pass an instance as a generic type parameter. That would make no sense.

This should create the new dictionary.

Code (csharp):

1.  
2. public Dictionary<string,  Dictionary<string,  Dictionary<string, string>>> globaldict = new Dictionary<string, Dictionary<string, Dictionary<string, string>>>();
3.  

Here is a nested dictionary with an example of how extension methods can be used to simplify adding new items. Similar extension methods could be made for removing or finding items.

Code (csharp):

1.  
2.  
3. public class DictionaryTest : MonoBehaviour {
4.  
5.     public Dictionary<string, Dictionary<string, Dictionary<string, string>>> dictionary
6.         = new Dictionary<string, Dictionary<string, Dictionary<string, string>>>();
7.  
8.     void Awake()
9.     {
10.         dictionary.Add("A", "B", "C", "Value");
11.  
12.         Debug.Log(dictionary["A"]["B"]["C"]);
13.     }
14. }
15.  
16. public static class DictionaryExtensions
17. {  
18.     public static void Add(
19.         this Dictionary<string, Dictionary<string, Dictionary<string, string>>> dictionary,
20.         string key1,
21.         string key2,
22.         string key3,
23.         string value
24.         )
25.     {
26.         Dictionary<string, Dictionary<string, string>> nested;
27.         if (dictionary.TryGetValue(key1, out nested))
28.             nested.Add(key2, key3, value);      
29.         else
30.         {
31.             nested = new Dictionary<string, Dictionary<string, string>>();
32.             nested.Add(key2, key3, value);
33.             dictionary.Add(key1, nested);
34.         }
35.     }
36.  
37.     public static void Add(
38.         this Dictionary<string, Dictionary<string, string>> dictionary,
39.         string key1,
40.         string key2,
41.         string value
42.         )
43.     {
44.         Dictionary<string, string> nested;
45.         if (dictionary.TryGetValue(key1, out nested))
46.             nested.Add(key2, value);
47.         else
48.         {
49.             nested = new Dictionary<string, string>();
50.             nested.Add(key2, value);
51.             dictionary.Add(key1, nested);
52.         }
53.     }
54. }
55.