Summary: in this tutorial, you’ll learn how to use C# generics to define reusable and type-neutral classes.
Introduction to the C# generic classes
The following shows the Stack class that allows you to push a string onto a stack or pop the top element out of it:
namespace CSharpTutorial; class Stack { int current = -1; string[] items; public Stack(int size) { items = new string[size]; } public bool Empty => current == -1; public bool Full => current == items.Length - 1; public bool Push(string item) { if (!Full) { items[++current] = item; return true; } return false; } public string? Pop() => !Empty ? items[current--] : null; }Code language: C# (cs)The Stack class works fine with strings. But if you want to have a stack of other types like integer, float, or objects, you need to create a class for each type.
To make the Stack class more generic and reusable, you can use C# generics to define a generic class. The following defines a generic Stack class that works with any type.
namespace CSharpTutorial; class Stack<T> { int current = -1; T[] items; public Stack(int size) { items = new T[size]; } public bool Empty => current == -1; public bool Full => current == items.Length - 1; public bool Push(T item) { if (!Full) { items[++current] = item; return true; } return false; } public T? Pop() => !Empty ? items[current--] : default(T); }Code language: C# (cs)How it works.
First, specify the type (T) inside angle brackets <> that follows the class name:
class Stack<T>Code language: C# (cs)Second, use the type (T) for the items member:
T[] items;Code language: C# (cs)Third, use the type (T) in the constructor, pop, and push methods.
The following shows how to use the Stack<T> class:
class Program { public static void Main(string[] args) { var colors = new Stack<string>(3); colors.Push("Red"); colors.Push("Green"); colors.Push("Blue"); while (true) { var color = colors.Pop(); if (color == null) { break; } Console.WriteLine(color); } } }Code language: C# (cs)How it works.
First, create a new instance of the Stack and specify the string as the type:
var colors = new Stack<string>(3);Code language: C# (cs)Second, call the Push() method three times to push the Red, Green, and Blue strings into the stack:
colors.Push("Red"); colors.Push("Green"); colors.Push("Blue");Code language: C# (cs)Third, pop the string out of the stack until it is empty by calling the Pop() method:
while (true) { var color = colors.Pop(); if (color == null) { break; } Console.WriteLine(color); }Code language: C# (cs)Summary
- Use C# generic class to build reusable and type-neutral classes.
