To rotate a matrix in spiral order, we need to do the following until all the inner matrix and the outer matrix are covered −

Step1 − Move elements of top row
Step2 − Move elements of last column
Step3 − Move elements of bottom row
Step4 − Move elements of first column
Step5 − Repeat above steps for inner ring while there is an inner matrix

using System;
namespace CsharpCode_ConsoleApplication{
   public class Matrix{
      public void PrintMatrixInSpiralOrder(int m, int n, int[,] a){
         int i, k = 0, l = 0;
         while (k < m && l < n){
            for (i = l; i < n; ++i){
               Console.Write(a[k, i] + " ");
            }
            k++;
            for (i = k; i < m; ++i){
               Console.Write(a[i, n - 1] + " ");
            }
            n--;
            if (k < m){
               for (i = n - 1; i >= l; --i){
                  Console.Write(a[m - 1, i] + " ");
               }
               m--;
            }
            if (l < n){
               for (i = m - 1; i >= k; --i){
                  Console.Write(a[i, l] + " ");
               }
               l++;
            }
         }
      }
   }
   class CsharpCode_Program{
      static void Main(string[] args){
         Matrix m = new Matrix();
         int R = 3;
         int C = 6;
         int[,] aa = { { 1, 2, 3, 4, 5, 6 },
            { 7, 8, 9, 10, 11, 12 },
            { 13, 14, 15, 16, 17, 18 } };
            m.PrintMatrixInSpiralOrder(R, C, aa);
      }
   }
}