What types of type casting exist in C#?

In C#, there are two main types of type casting:

1. Explicit conversion: Requires the use of the cast operator (type). It is used when the compiler cannot safely perform the conversion automatically, for example, when casting from a base class to a derived class or from a higher precision type to a lower one (e.g., double to int). It can lead to data loss or runtime errors (InvalidCastException).

   // Explicit cast from double to int
   double d = 123.45;
   int i = (int)d; // i will be 123
   
   // Explicit cast of an object to a specific type
   object obj = "Hello";
   string s = (string)obj; // s will be "Hello"
   

2. Implicit conversion: Performed automatically by the compiler when the conversion is known and safe, meaning no data loss occurs. For example, casting from int to double.

   // Implicit cast from int to double
   int x = 10;
   double y = x; // y will be 10.0
   
   // Implicit cast from a derived class to a base class
   class Base {}
   class Derived : Base {}
   
   Derived derivedObj = new Derived();
   Base baseObj = derivedObj; // Implicit cast
   

Additionally, there are the as and is operators, which are also related to type casting but with specific features:

• as operator: Performs a cast if possible and returns null if the cast fails. It does not throw an InvalidCastException. It is only used for reference types and nullable types.

  // Using the `as` operator
  object obj2 = "World";
  string s2 = obj2 as string; // s2 will be "World"
  
  object obj3 = 123;
  string s3 = obj3 as string; // s3 will be null
  

• is operator: Checks whether an object is an instance of a specific type or derived from it. Returns true or false. In recent C# versions, it can be used with pattern matching for simultaneous type checking and casting.

  // Using `is` to check type
  object obj4 = "Example";
  if (obj4 is string)
  {
      // Actions if the object is a string
  }
  
  // Using `is` with pattern matching
  if (obj4 is string str)
  {
      // str is accessible here as a string
  }