What is the easiest way to handle associative array in c#?

Use the Dictionary class. It should do what you need. Reference is here.

So you can do something like this:

IDictionary<string, int> dict = new Dictionary<string, int>();
dict["red"] = 10;
dict["blue"] = 20;

A dictionary will work, but .NET has associative arrays built in. One instance is the NameValueCollection class (System.Collections.Specialized.NameValueCollection).

A slight advantage over dictionary is that if you attempt to read a non-existent key, it returns null rather than throw an exception. Below are two ways to set values.

NameValueCollection list = new NameValueCollection();
list["key1"] = "value1";

NameValueCollection list2 = new NameValueCollection()
{
    { "key1", "value1" },
    { "key2", "value2" }
};