_=> what does this underscore mean in Lambda expressions?

Question

What does an lambda expression like _=> expr mean?

What is the purpose of _ as input to lambda?

Example:

int cou         


        

Answer 1

Because lamda expression is mostly used in a short, anonymous code so that the name of the variable sometimes is not neccessary, even they do not use the variable in the code block, so that they just give a _ for a short, convention