Write a C# console application on visual studio that reads a students grade and displays the letter grade. It should validate the input before processing it, i.e. if the input is negative or more than 100, output an error message and stop the program. If the input is not a number, output an error message and stop the program, too. There is one requirement: to determine the letter grade, use switchcase

100>=grade>=90 A

90>grade>=80 B

80>grade>=70 C

70>grade>=60 D

Grade<60 F