Time to put on our detective caps: using deductive reasoning, we can make our lambda expression even shorter. Here’s what we have to start:

bool hasEvenNumbers = Array.Exists(numbers, (int num) => num % 2 == 0 );

The type of num is int. It’s great to be explicit like this to avoid errors, but some developers wouldn’t include int. To them, it’s obvious! Here’s their reasoning:

  • The modulo operator (%) is only used with numbers, so num must be a number
  • The result of the operation num % 2 is compared to the integer 0. We can only compare similar types, so num must also be an integer!

Therefore, we can remove int without causing any errors:

bool hasEvenNumbers = Array.Exists(numbers, (num) => num % 2 == 0 );

When there is just one parameter in a lambda expression, we don’t need the parentheses around the parameter either:

bool hasEvenNumbers = Array.Exists(numbers, num => num % 2 == 0 );

We just learned two new shortcuts “within” the lambda expression shortcut. Though we don’t need to use them all the time, we do need to recognize them in other developers’ code:

  1. We can remove the parameter type if it can be inferred
  2. We can remove the parentheses if there is one parameter



Apply the first shortcut to the lambda expression (remove the parameter type).


Apply the second shortcut to the lambda expression (remove the parentheses).

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