A reference constriant : Type constaint « Generic « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Generic
3. Type constaint

using System; 
 
class MyClass { 
} 
 
class Test<T> where T : class { 
  T obj; 
 
  public Test() { 
    // Here T must be a reference type, 
    // which can be assigned the value null. 
    obj = null; 
  } 
} 
 
class MainClass { 
  public static void Main() { 
    // The following is OK because MyClass is a class. 
    Test<MyClass> x = new Test<MyClass>(); 
 
    // The next line is in error because int is a value type. 
    // Test<int> y = new Test<int>(); 
  } 
}