Why is the matrix not transposed?

Question

C++ / C#

public static int[,] getTransposeMatrix(int[,] matrix)
            {
                int[,] resMatrix = matrix;

                for (int i = 0; i < resMatrix.GetLength(0); i++)
                {
                    for (int j = 0; j < resMatrix.GetLength(1); j++)
                    {
                        int tmp = resMatrix[i, j];
                        resMatrix[i, j] = resMatrix[j, i];
                        resMatrix[j, i] = tmp;
                    }
                }

                return resMatrix;
            }

Obviously a silly mistake, but I can't find it.

Answer 1

because you completely enumerate it, as a result, the exchange occurs twice
ps and if you try to transpose a non-square matrix with this code, you will catch a crash in general. meditate on it ;)