How can I create a list and look up a value in C#

I would like to implement some kind of a look up in C# but I am not sure how to do this.

I have a variable that can have a value of between 0 and 9. For each variable there will be a text string that goes with it.

I guess I need to set up some kind of list.

A really simple example on how I could access the list and how I could populate the开发者_运维技巧 list would be much appreciated.

I tried the following:

public static class RefData
{
    public static Dictionary<int, string> dict = new Dictionary<int, string>();
    dict.Add(0, "This Text");
    dict.Add(3, "That Text");
    dict.Add(4, "More Text");
}

but it gives an error message saying "can't resolve symbol dict on the lines with the dict.Add

---

This is an answer to the updated question. The problem with your current code is that you're trying to execute statements without them being inside a method, property, constructor etc. You can't do that. There are two obvious options here. First, you can use a method to build your dictionary:

public static class RefData
{
    private static readonly Dictionary<int, string> dict = BuildDictionary();

    private static Dictionary<int, string> BuildDictioary()
    {
        Dictionary<int, string> ret = new Dictionary<int, string>();
        ret.Add(0, "This Text");
        ret.Add(3, "That Text");
        ret.Add(4, "More Text");
        return ret;
    }
}

The other is to use a collection initializer if you're using C# 3 or higher:

public static class RefData
{
    private static readonly Dictionary<int, string> dict = 
        new Dictionary<int, string>
    {
        { 0, "This Text" },
        { 3, "That Text" },
        { 4, "More Text" }
    };
}

Note how in both cases I've made the variable private and read-only. You should almost never expose fields publicly - particularly mutable ones. You'll probably want to provide appropriate methods which act on the dictionary - and remember that Dictionary is not thread-safe.

---

You're trying to put code inside of a class definition. You need to move your dict.Add() calls either in a method or a static constructor. Something like:

public static class RefData
{
    public static Dictionary<int, string> dict = new Dictionary<int, string>();

    static Refdata() //this could also be: public static void PopulateDictionary()
    {
        dict.Add(0, "This Text");
        dict.Add(3, "That Text");
        dict.Add(4, "More Text"); 
    }
}

You can do that if you want to fill it with default data, I suppose, you can always add or remove keys from it later from other parts of your code, since its a public static member.

---

A generic dictionary. Something like:

 Dictionary<int, string> dict = new Dictionary<int, string>()

The first type, int is your key. Each key has to be unique, and will have a string value.

If you did something like this:

 dict.Add(0, "This Text");
 dict.Add(3, "That Text");
 dict.Add(4, "More Text");

you could look up the value like this:

 string value = dict[3];  //returns "That Text"

If a key already exists in the dictionary, the add will fail. As in you can't do this twice:

 dict.Add(3, "That Text");
 dict.Add(3, "More Text");

As I said before, the key (in this case your int) has to be unique. You can reassign the value by doing

 dict[3] = "New Text"

The great thing about a generic dictionary, is that it can hold any type you want! The definition of the dictionary is Dictionary<Tkey, TValue>, you get to specify the types, and you can set them to whatever you want.

---

You can use the Dictionary class in System.Collections.Generic

Dictionary<byte, string> dct = new Dictionary<byte, string>();

You can add values to the dictionary like this

dct.Add(0, "Some Value");

you can access the values in dictionary like this

string val = dct[0];

---

I have a variable that can have a value of between 0 and 9. For each variable there will be a text string that goes with it. 

This means that you need a dictionary. You can use many specialized dictionaries in .NET. But my recommendation is to use:

Dictionary<int, string> list = new Dictionary<int, string>();

To check if the list already contains something or not, simply use:

list.ContainsKey(someIntHere);

To get the string value of the specified key, simply use:

string value = list[key];

---

The dictionary class is your friend here.

e.g.

var textByNumber = new Dictionary<int, string>();    
textByNumber[0] = "Alice";    
textByNumber[1] = "Bob";

And to retrive a value, you can go:

var text = textByNumber[1];