Wednesday, December 19, 2007

Generic Dictionary in C#

[This was originally posted at]

I love the generic Dictionary class. It's located in the System.Collections.Generic namespace. This class is like a strongly-typed hash table (which lets you reference objects as key-value pairs). You can specify the type for the key and another type for the value. This code snippet below shows how to create, add, and retrieve data from a Dictionary. It spares the developer from writing a bunch of extra conversion wrapping code.

    public void Dictionary_1()
      Dictionary<string, DateTime> group = new Dictionary<string, DateTime>();

      //Add based on separate variables
      string strKey1 = "abc";
      DateTime dt1 = DateTime.Now;
      group.Add(strKey1, dt1);

      //Add as single line
      group.Add("def", new DateTime(2005, 12, 25));

      //Should now have 2 items
      Assert.AreEqual(2, group.Count);

      //Get value given key
      DateTime dt2 = group["abc"];
      Assert.AreEqual(dt1, dt2);

Generics are great. You can also use them for strongly-typed lists, setting the return type of a method, and many other techniques that simplify code.

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