Using params keyword

Let’s say you have a class and you want to store a collection of strings in that class. How would your method look like which would let you add a string to the class?

   1: public class SampleClass

   2:  {

   3:      private List<string> myList = null; 

   4:  

   5:      public SampleClass()

   6:      {

   7:          myList = new List<string>(); 

   8:      }

   9:  }

There are a couple of ways you could write the method; it also depends on what are you trying to achieve. Below are some of the samples how you could do this (yes, I know, there are probably million other ways to do this :)):

   1: public void AddItem(string item)

   2: {

   3:     // Do something 

   4: }

   5:  

   6: public void AddItems(List<string> items)

   7: { 

   8:     // Do something 

   9: }

  10:  

  11: public void AddItems (string [] items) 

  12: {

  13:     // Do something 

  14: }

Every method above has it’s benefits and drawbacks – I have to pass in an array of string, I can only pass in one string a the time, sometimes I want to pass in 3 strings and sometimes 1 – why can’t I use one method only?).

There’s a keyword called “params” you could use to solve this problem – with this keyword you can pass in as many parameters as you like; for example all calls below are made to the same method:

   1: SampleClass my = new SampleClass();

   2: my.AddItems("One"); 

   3: my.AddItems("One", "Two");

   4: my.AddItems("One", "Two", "Three"); 

And here’s how the method would look like:

   1: public void AddItems(params string[] items)

   2: {

   3:     foreach (string item in items)

   4:     { 

   5:         // Do something

   6:     }

   7: }