nxn matrix

public static int[,] GenerateMatrix(int n)
{
    int[,] matrix = new int[n, n];

    for (int row = 0; row < n; row++)
    {
        for (int col = 0; col < n; col++)
        {
            matrix[row, col] = row + col;
        }
    }

    return matrix;
}

public static string PrintMatrix(int[,] matrix)
{
    StringBuilder output = new StringBuilder();
    int n = matrix.GetLength(0);

    for (int row = 0; row < n; row++)
    {
        for (int col = 0; col < n; col++)
        {
            output.Append(matrix[row, col] + " ");
        }

        output.AppendLine();
    }

    return output.ToString().TrimEnd();
}