how to fix Index Out Of Range Exception

I made this code for the king in a chess game. Whenever the king is on the very right or left side of the board, I get the "IndexOutOfRangeException" error. Anyone know how to fix?

 using UnityEngine;
 using System.Collections;
 
 public class King : Chessman
 {
     public override bool[,] PossibleMove()
     {
         bool[,] r = new bool[8, 8];
 
         Chessman c;
         int i, j;
 
         //Top Side
         i = CurrentX - 1;
         j = CurrentY + 1;
         if (CurrentY != 7)
         {
             for (int k = 0; k < 3; k++)
             {
                 if (i >= 0 || i < 8)
                 {
                     c = BoardManager.Instance.Chessmans[i, j];
                     if (c == null)
                         r[i, j] = true;
                     else if (isWhite != c.isWhite)
                         r[i, j] = true;
                 }
 
                 i++;
             }
         }
 
         //Down Side
         i = CurrentX - 1;
         j = CurrentY - 1;
         if (CurrentY != 0)
         {
             for (int k = 0; k < 3; k++)
             {
                 if (i >= 0 || i < 8)
                 {
                     c = BoardManager.Instance.Chessmans[i, j];
                     if (c == null)
                         r[i, j] = true;
                     else if (isWhite != c.isWhite)
                         r[i, j] = true;
                 }
 
                 i++;
             }
         }
 
         //Midlle Left
         if (CurrentX != 0)
         {
             c = BoardManager.Instance.Chessmans[CurrentX - 1, CurrentY];
             if (c == null)
                 r[CurrentX - 1, CurrentY] = true;
             else if (isWhite != c.isWhite)
                 r[CurrentX - 1, CurrentY] = true;
         }
 
         //Midlle Right
         if (CurrentX != 7)
         {
             c = BoardManager.Instance.Chessmans[CurrentX + 1, CurrentY];
             if (c == null)
                 r[CurrentX + 1, CurrentY] = true;
             else if (isWhite != c.isWhite)
                 r[CurrentX + 1, CurrentY] = true;
         }
 
         return r;
     }
 }