While exceptions have always existed in C# the throw keyword was only treated as a statement which meant it could not be used in places where only expressions were allowed such as inside a conditional or coalescing operator.

C# 7.0 introduces throw expressions which allow exceptions to be thrown in more convenient ways.

Code

Now

void ProcessAdult(string name, age)
{
  var requiredName = name ?? throw new ArgumentNullException(nameof(name));
  var adultAge = age >= 18 ? age : throw new ArgumentOutOfRangeException(nameof(age));

  // ...
}

Before

void ProcessAdult(string name, age)
{
  if (name == null)
  {
    throw new ArgumentNullException(nameof(name));
  }
  var requiredName = name;

  if (age < 18)
  {
    throw new ArgumentOutOfRangeException(nameof(age));
  }
  var adultAge = age;

  // ...
}

More information

• What's new in C# 7.0