Major and importance difference between for and foreach loop ?

yes

For Loop static int Method1(int[] array) { int a = 0; for (int i = 0; i < array.Length; i++) { a += array[i]; } return a; } Foreach loop static int Method2(int[] array) { int a = 0; foreach (int value in array) { a += value; } return a; }

a for loop is a construct that says "perform this operation n. times". a foreach loop is a construct that says "perform this operation against each value/object in this IEnumerable"