c# - Inputting a number beyond a range set by an array, index out of range error -

i want make program wherein user inputs number, in case number of items. number of items compared value in array, , corresponding discount displayed.

using system; using system.collections.generic; using system.linq; using system.text;  namespace consoleapplication11 {     class program     {         const int size = 4;         static void main(string[] args)         {             int itemsbought = 0;             int discountitem = 0;             int[] items = new int[size] { 0, 10, 26, 61 };             int[] discount = new int[size] { 0, 5, 10,15 };              inputitems(ref itemsbought);             getdiscount(items, discount, ref itemsbought, ref discountitem);              console.writeline("your discount {0}", discountitem);          }          private static void getdiscount(int[] items, int[] discount, ref int itemsbought, ref int discountitem)         {             int idx = 0;             (idx = 0; itemsbought > items[idx] || idx > items.length; idx++)             {                      discountitem = discount[idx];             }             }          private static void inputitems(ref int itemsbought)         {             console.writeline("enter amount of items bought");             while (!int.tryparse(console.readline(), out itemsbought))                 if (itemsbought < 0)              {                     console.writeline("error, whole numbers on 0 only");             }                 console.writeline("error, whole numbers on 0 only");         }     } } 

when number above 61 entered "index out of range" error. how can make if number above 61 entered, displays 15? how can boundary includes 61 , on instead of 61 giving output of 10?

also everytime enter gives error message shown displays when number less 0 or double.

to show small error made, see corrected version:

for (idx = 0; idx < items.length && itemsbought > items[idx]; idx++) 

there 3 important changes:

1. idx > items.length false. , idx= items.length out-of-range.
2. use && instead of || remember if condition true, loop continued execution, false once, execution stopped.
3. exchanged order. must check idx < items.length before accessing items[idx]. shortcircuit && evaluates left right , stops if result determined.

so corrected code this:

private static void getdiscount(int[] items, int[] discount, int itemsbought, ref int discountitem) {     int idx = 0;     (idx = 0; idx < items.length && itemsbought > items[idx]; idx++)         discountitem = discount[idx]; } 

but i'd prefer put condition inside loop make more readable:

private static void getdiscount(int[] items, int[] discount, int itemsbought, ref int discountitem) {     (int = 0; < items.length; i++)     {         if(itemsbought > items[i])             discountitem = discount[i];         else             break;     } } 

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to address other issue

also everytime enter gives error message shown displays when number less 0 or double.

reformat code properly, 1 message output in right place, other 1 executed.