Month: January 2015

Have you ever wanted to walk through all of the open handles across all processes that are active on a Windows machine and even be able to do things like close specific handles that those processes have open? I sure have, and I did…but more specifically for my needs I wanted to know what processes had file handles open to specific files on my machine, or what processes had locked specific folders, and so forth. The following code snippet I am going to share is working code, complete with a nice unmanaged library wrapper in case you want to use it through the CLR with your favourite C# projects. It calls on some very low level APIs. These APIs are not your run of the mill, Windows application-friendly type of APIs, so be warned that like all other code on my site, you are responsible for what you do with it. I take no responsibility for any damages. If you happen to bring open handles to a close, that could result in a system-wide catastrophe, the results of which are completely unpredictable relative to what process had that handle open.

UnmanagedLibrary.h:

#include <windows.h>
#include <TlHelp32.h>
#include <iostream>
#include <sstream>
#include <map>
#include <vector>

using namespace std;

void CheckForLocks(wstring fullPath, vector<unsigned long> *processes);
bool CloseHandles(wstring fullPath, int process);

UnmanagedLibrary.cpp:

#include "UnmanagedLibrary.h"

#define NT_SUCCESS(x) ((x) >= 0)
#define STATUS_INFO_LENGTH_MISMATCH 0xc0000004
#define SystemHandleInformation 16
#define ObjectBasicInformation 0
#define ObjectNameInformation 1
#define ObjectTypeInformation 2

typedef NTSTATUS(NTAPI *_NtQuerySystemInformation)(ULONG SystemInformationClass, PVOID SystemInformation, ULONG SystemInformationLength, PULONG ReturnLength);
typedef NTSTATUS(NTAPI *_NtDuplicateObject)(HANDLE SourceProcessHandle, HANDLE SourceHandle, HANDLE TargetProcessHandle, PHANDLE TargetHandle, ACCESS_MASK DesiredAccess, ULONG Attributes, ULONG Options);
typedef NTSTATUS(NTAPI *_NtQueryObject)(HANDLE ObjectHandle, ULONG ObjectInformationClass, PVOID ObjectInformation, ULONG ObjectInformationLength, PULONG ReturnLength);

typedef struct _UNICODE_STRING
{
	USHORT Length;
	USHORT MaximumLength;
	PWSTR Buffer;
} UNICODE_STRING, *PUNICODE_STRING;

typedef struct _SYSTEM_HANDLE
{
	ULONG ProcessId;
	BYTE ObjectTypeNumber;
	BYTE Flags;
	USHORT Handle;
	PVOID Object;
	ACCESS_MASK GrantedAccess;
} SYSTEM_HANDLE, *PSYSTEM_HANDLE;

typedef struct _SYSTEM_HANDLE_INFORMATION
{
	ULONG HandleCount;
	SYSTEM_HANDLE Handles[1];
} SYSTEM_HANDLE_INFORMATION, *PSYSTEM_HANDLE_INFORMATION;

typedef enum _POOL_TYPE
{
	NonPagedPool,
	PagedPool,
	NonPagedPoolMustSucceed,
	DontUseThisType,
	NonPagedPoolCacheAligned,
	PagedPoolCacheAligned,
	NonPagedPoolCacheAlignedMustS
} POOL_TYPE, *PPOOL_TYPE;

typedef struct _OBJECT_TYPE_INFORMATION
{
	UNICODE_STRING Name;
	ULONG TotalNumberOfObjects;
	ULONG TotalNumberOfHandles;
	ULONG TotalPagedPoolUsage;
	ULONG TotalNonPagedPoolUsage;
	ULONG TotalNamePoolUsage;
	ULONG TotalHandleTableUsage;
	ULONG HighWaterNumberOfObjects;
	ULONG HighWaterNumberOfHandles;
	ULONG HighWaterPagedPoolUsage;
	ULONG HighWaterNonPagedPoolUsage;
	ULONG HighWaterNamePoolUsage;
	ULONG HighWaterHandleTableUsage;
	ULONG InvalidAttributes;
	GENERIC_MAPPING GenericMapping;
	ULONG ValidAccess;
	BOOLEAN SecurityRequired;
	BOOLEAN MaintainHandleCount;
	USHORT MaintainTypeList;
	POOL_TYPE PoolType;
	ULONG PagedPoolUsage;
	ULONG NonPagedPoolUsage;
} OBJECT_TYPE_INFORMATION, *POBJECT_TYPE_INFORMATION;

using namespace std;

PVOID GetLibraryProcAddress(PSTR LibraryName, PSTR ProcName)
{
	return GetProcAddress(GetModuleHandleA(LibraryName), ProcName);
}

_NtQuerySystemInformation NtQuerySystemInformation = (_NtQuerySystemInformation)GetLibraryProcAddress("ntdll.dll", "NtQuerySystemInformation");
_NtDuplicateObject NtDuplicateObject = (_NtDuplicateObject)GetLibraryProcAddress("ntdll.dll", "NtDuplicateObject");
_NtQueryObject NtQueryObject = (_NtQueryObject)GetLibraryProcAddress("ntdll.dll", "NtQueryObject");

struct QueryStructure
{
	HANDLE dupHandle;
	PVOID objectNameInfo;
	ULONG objectInfoLength;
	ULONG returnLength;
	NTSTATUS result;
};

HANDLE beginQuery = CreateEvent(0, FALSE, FALSE, 0);
HANDLE endQuery = CreateEvent(0, FALSE, FALSE, 0);
QueryStructure queryStructure;

HANDLE beginQueryCloseHandle = CreateEvent(0, FALSE, FALSE, 0);
HANDLE endQueryCloseHandle = CreateEvent(0, FALSE, FALSE, 0);
QueryStructure queryStructureCloseHandle;

DWORD WINAPI queryThread(LPVOID parameter)
{
	while (WaitForSingleObject(beginQuery, INFINITE) == WAIT_OBJECT_0)
	{
		queryStructure.result = NtQueryObject(queryStructure.dupHandle, ObjectNameInformation, queryStructure.objectNameInfo, queryStructure.objectInfoLength, &queryStructure.returnLength);
		SetEvent(endQuery);
	}
	return 0;
}

DWORD WINAPI queryThreadCloseHandle(LPVOID parameter)
{
	while (WaitForSingleObject(beginQueryCloseHandle, INFINITE) == WAIT_OBJECT_0)
	{
		queryStructureCloseHandle.result = NtQueryObject(queryStructureCloseHandle.dupHandle, ObjectNameInformation, queryStructureCloseHandle.objectNameInfo, queryStructureCloseHandle.objectInfoLength, &queryStructureCloseHandle.returnLength);
		SetEvent(endQueryCloseHandle);
	}
	return 0;
}

HANDLE queryThreadHandle = CreateThread(0, 0, &queryThread, 0, 0, 0);
HANDLE queryThreadCloseHandleHandle = CreateThread(0, 0, &queryThreadCloseHandle, 0, 0, 0);

void ConvertPath(wstring *path, map<wstring, wstring> *volumes)
{
	for (map<wstring, wstring>::iterator i = (*volumes).begin(); i != (*volumes).end(); ++i)
	{
		if ((*path).compare(0, (*i).first.size(), (*i).first) == 0)
		{
			*path = (*path).replace(0, (*i).first.size(), (*i).second);
			break;
		}
	}
}

void CheckForLocks(wstring fullPath, vector<unsigned long> *processes)
{
	DWORD	CharCount = 0;
	WCHAR	DeviceName[MAX_PATH] = L"";
	HANDLE	FindHandle = INVALID_HANDLE_VALUE;
	size_t	Index = 0;
	BOOL	Success = FALSE;
	WCHAR	VolumeName[MAX_PATH] = L"";
	map<wstring, wstring> volumes;
	FindHandle = FindFirstVolumeW(VolumeName, ARRAYSIZE(VolumeName));
	while (true)
	{
		Index = wcslen(VolumeName) - 1;
		if (VolumeName[0] != L'\\' || VolumeName[1] != L'\\' || VolumeName[2] != L'?' || VolumeName[3] != L'\\' || VolumeName[Index] != L'\\')
		{
			break;
		}
		VolumeName[Index] = L'\0';
		CharCount = QueryDosDeviceW(&VolumeName[4], DeviceName, ARRAYSIZE(DeviceName));
		VolumeName[Index] = L'\\';
		if (CharCount == 0)
		{
			break;
		}
		DWORD	size = MAX_PATH + 1;
		PWCHAR	name = NULL;
		BOOL	success = FALSE;
		while (!success)
		{
			name = (PWCHAR) new BYTE[size * sizeof(WCHAR)];
			success = GetVolumePathNamesForVolumeNameW(VolumeName, name, size, &size);
			if (!success)
			{
				delete[] name;
				name = NULL;
			}
		}
		volumes[DeviceName + wstring(L"\\")] = name;
		if (name != NULL)
		{
			delete[] name;
			name = NULL;
		}
		Success = FindNextVolumeW(FindHandle, VolumeName, ARRAYSIZE(VolumeName));
		if (!Success)
		{
			if (GetLastError() != ERROR_NO_MORE_FILES)
			{
				break;
			}
			break;
		}
	}
	FindVolumeClose(FindHandle);
	FindHandle = INVALID_HANDLE_VALUE;
	NTSTATUS status;
	PSYSTEM_HANDLE_INFORMATION handleInfo;
	ULONG handleInfoSize = 0x10000;
	HANDLE processHandle;
	ULONG i;
	DWORD pid;
	HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
	PROCESSENTRY32 process;
	ZeroMemory(&process, sizeof(process));
	process.dwSize = sizeof(process);
	if (Process32First(snapshot, &process))
	{
		do
		{
			pid = process.th32ProcessID;
			if (!(processHandle = OpenProcess(PROCESS_DUP_HANDLE, FALSE, pid)))
			{
				continue;
			}
			handleInfo = (PSYSTEM_HANDLE_INFORMATION)malloc(handleInfoSize);
			while ((status = NtQuerySystemInformation(SystemHandleInformation, handleInfo, handleInfoSize, NULL)) == STATUS_INFO_LENGTH_MISMATCH)
			{
				handleInfo = (PSYSTEM_HANDLE_INFORMATION)realloc(handleInfo, handleInfoSize *= 2);
			}
			if (!NT_SUCCESS(status))
			{
				return;
			}
			for (i = 0; i < handleInfo->HandleCount; i++)
			{
				SYSTEM_HANDLE handle = handleInfo->Handles[i];
				HANDLE dupHandle = NULL;
				POBJECT_TYPE_INFORMATION objectTypeInfo;
				PVOID objectNameInfo;
				UNICODE_STRING objectName;
				ULONG returnLength = 0;
				if (handle.ProcessId != pid)
					continue;
				if (!NT_SUCCESS(NtDuplicateObject(processHandle, (HANDLE)handle.Handle, GetCurrentProcess(), &dupHandle, 0, 0, 0)))
				{
					continue;
				}
				objectTypeInfo = (POBJECT_TYPE_INFORMATION)malloc(0x1000);
				size_t currentSize = 0x1000;
				objectNameInfo = malloc(currentSize);
				queryStructure.dupHandle = dupHandle;
				queryStructure.objectNameInfo = objectNameInfo;
				queryStructure.objectInfoLength = 0x1000;
				queryStructure.returnLength = returnLength;
				queryStructure.result = -1;
				SetEvent(beginQuery);
				if (WaitForSingleObject(endQuery, 100) == WAIT_TIMEOUT)
				{
					TerminateThread(queryThreadHandle, 1);
					CloseHandle(queryThreadHandle);
					queryThreadHandle = CreateThread(0, 0, &queryThread, 0, 0, 0);
					CloseHandle(dupHandle);
					continue;
				}
				if (!NT_SUCCESS(queryStructure.result))
				{
					objectNameInfo = realloc(objectNameInfo, currentSize *= 2);
					if (!NT_SUCCESS(NtQueryObject(dupHandle, ObjectNameInformation, objectNameInfo, returnLength, NULL)))
					{
						free(objectTypeInfo);
						free(objectNameInfo);
						CloseHandle(dupHandle);
						continue;
					}
				}
				objectName = *(PUNICODE_STRING)objectNameInfo;
				if (objectName.Length)
				{
					wstring objectNameAsWString = wstring(objectName.Buffer, objectName.Length / sizeof(WCHAR));
					ConvertPath(&objectNameAsWString, &volumes);
					if ((int)objectNameAsWString.find(fullPath) >= 0)
					{
						(*processes).push_back(pid);
						free(objectTypeInfo);
						free(objectNameInfo);
						CloseHandle(dupHandle);
						break;
					}
				}
				free(objectTypeInfo);
				free(objectNameInfo);
				CloseHandle(dupHandle);
			}
			free(handleInfo);
			CloseHandle(processHandle);
		} while (Process32Next(snapshot, &process));
	}
}

bool CloseHandles(wstring fullPath, int process)
{
	DWORD	CharCount = 0;
	WCHAR	DeviceName[MAX_PATH] = L"";
	HANDLE	FindHandle = INVALID_HANDLE_VALUE;
	size_t	Index = 0;
	BOOL	Success = FALSE;
	WCHAR	VolumeName[MAX_PATH] = L"";
	map<wstring, wstring> volumes;
	FindHandle = FindFirstVolumeW(VolumeName, ARRAYSIZE(VolumeName));
	while (true)
	{
		Index = wcslen(VolumeName) - 1;
		if (VolumeName[0] != L'\\' || VolumeName[1] != L'\\' || VolumeName[2] != L'?' || VolumeName[3] != L'\\' || VolumeName[Index] != L'\\')
		{
			break;
		}
		VolumeName[Index] = L'\0';
		CharCount = QueryDosDeviceW(&VolumeName[4], DeviceName, ARRAYSIZE(DeviceName));
		VolumeName[Index] = L'\\';
		if (CharCount == 0)
		{
			break;
		}
		DWORD	size = MAX_PATH + 1;
		PWCHAR	name = NULL;
		BOOL	success = FALSE;
		while (!success)
		{
			name = (PWCHAR) new BYTE[size * sizeof(WCHAR)];
			success = GetVolumePathNamesForVolumeNameW(VolumeName, name, size, &size);
			if (!success)
			{
				delete[] name;
				name = NULL;
			}
		}
		volumes[DeviceName + wstring(L"\\")] = name;
		if (name != NULL)
		{
			delete[] name;
			name = NULL;
		}
		Success = FindNextVolumeW(FindHandle, VolumeName, ARRAYSIZE(VolumeName));
		if (!Success)
		{
			if (GetLastError() != ERROR_NO_MORE_FILES)
			{
				break;
			}
			break;
		}
	}
	FindVolumeClose(FindHandle);
	FindHandle = INVALID_HANDLE_VALUE;
	_NtQuerySystemInformation NtQuerySystemInformation = (_NtQuerySystemInformation)GetLibraryProcAddress("ntdll.dll", "NtQuerySystemInformation");
	_NtDuplicateObject NtDuplicateObject = (_NtDuplicateObject)GetLibraryProcAddress("ntdll.dll", "NtDuplicateObject");
	_NtQueryObject NtQueryObject = (_NtQueryObject)GetLibraryProcAddress("ntdll.dll", "NtQueryObject");
	NTSTATUS status;
	PSYSTEM_HANDLE_INFORMATION handleInfo;
	ULONG handleInfoSize = 0x10000;
	HANDLE processHandle;
	ULONG i;
	if (!(processHandle = OpenProcess(PROCESS_DUP_HANDLE, FALSE, process)))
	{
		return false;
	}
	handleInfo = (PSYSTEM_HANDLE_INFORMATION)malloc(handleInfoSize);
	while ((status = NtQuerySystemInformation(SystemHandleInformation, handleInfo, handleInfoSize, NULL)) == STATUS_INFO_LENGTH_MISMATCH)
	{
		handleInfo = (PSYSTEM_HANDLE_INFORMATION)realloc(handleInfo, handleInfoSize *= 2);
	}
	if (!NT_SUCCESS(status))
	{
		return false;
	}
	for (i = 0; i < handleInfo->HandleCount; i++)
	{
		SYSTEM_HANDLE handle = handleInfo->Handles[i];
		HANDLE dupHandle = NULL;
		POBJECT_TYPE_INFORMATION objectTypeInfo;
		PVOID objectNameInfo;
		UNICODE_STRING objectName;
		ULONG returnLength = 0;
		if (handle.ProcessId != process)
			continue;
		if (!NT_SUCCESS(NtDuplicateObject(processHandle, (HANDLE)handle.Handle, GetCurrentProcess(), &dupHandle, 0, 0, 0)))
		{
			continue;
		}
		objectTypeInfo = (POBJECT_TYPE_INFORMATION)malloc(0x1000);
		size_t currentSize = 0x1000;
		objectNameInfo = malloc(currentSize);
		queryStructureCloseHandle.dupHandle = dupHandle;
		queryStructureCloseHandle.objectNameInfo = objectNameInfo;
		queryStructureCloseHandle.objectInfoLength = 0x1000;
		queryStructureCloseHandle.returnLength = returnLength;
		queryStructureCloseHandle.result = -1;
		SetEvent(beginQueryCloseHandle);
		if (WaitForSingleObject(endQueryCloseHandle, 100) == WAIT_TIMEOUT)
		{
			TerminateThread(queryThreadCloseHandleHandle, 1);
			CloseHandle(queryThreadCloseHandleHandle);
			queryThreadCloseHandleHandle = CreateThread(0, 0, &queryThreadCloseHandle, 0, 0, 0);
			CloseHandle(dupHandle);
			continue;
		}
		if (!NT_SUCCESS(queryStructureCloseHandle.result))
		{
			objectNameInfo = realloc(objectNameInfo, currentSize *= 2);
			if (!NT_SUCCESS(NtQueryObject(dupHandle, ObjectNameInformation, objectNameInfo, returnLength, NULL)))
			{
				free(objectTypeInfo);
				free(objectNameInfo);
				CloseHandle(dupHandle);
				continue;
			}
		}
		objectName = *(PUNICODE_STRING)objectNameInfo;
		if (objectName.Length)
		{
			wstring objectNameAsWString = wstring(objectName.Buffer, objectName.Length / sizeof(WCHAR));
			ConvertPath(&objectNameAsWString, &volumes);
			if ((int)objectNameAsWString.find(fullPath) >= 0)
			{
				NtDuplicateObject(processHandle, (HANDLE)handle.Handle, 0, 0, 0, 0, 1);
			}
		}
		free(objectTypeInfo);
		free(objectNameInfo);
		CloseHandle(dupHandle);
	}
	free(handleInfo);
	CloseHandle(processHandle);
	return true;
}

Note: The two most important methods above are firstly, CheckForLocks, which takes either a system drive path, file path, or folder path, and returns a vector of processes with open handles at the given path, and secondly CloseHandles, which takes the same types of paths and a process ID. CloseHandles closes any open handles (containing the specified path) of a target process via a specified process ID. Below, I will even include some code to produce a CLR wrapper around this Static Library so that you can call it from C#.

Unmanaged.h:

#include "..\UnmanagedLibrary\UnmanagedLibrary.h"

using namespace System;
using namespace System::Collections::Generic;

namespace Unmanaged
{
	public ref class Handles
	{
	public:
		static List<int>^ GetProcessesWithOpenHandlesToPath(String^ path);
		static bool CloseOpenHandlesToPathInProcess(String^ path, int process);
	};
}

Unmanaged.cpp:

#include "Unmanaged.h"
#include "msclr\marshal_cppstd.h"

List<int>^ Unmanaged::Handles::GetProcessesWithOpenHandlesToPath(String^ path)
{
	List<int>^ list = gcnew List<int>();
	wstring convertedString = msclr::interop::marshal_as<wstring>(path);
	vector<unsigned long> processes;
	CheckForLocks(convertedString, &processes);
	for (vector<unsigned long>::iterator i = processes.begin(); i != processes.end(); i++) {
		list->Add(*i);
	}
	return list;
}

bool Unmanaged::Handles::CloseOpenHandlesToPathInProcess(String^ path, int process)
{
	List<int>^ list = gcnew List<int>();
	wstring convertedString = msclr::interop::marshal_as<wstring>(path);
	return CloseHandles(convertedString, process);
}

From C#, you simply call these two functions of the Unmanaged DLL:

List<int> processes = Unmanaged.Handles.GetProcessesWithOpenHandlesToPath(path);
Unmanaged.Handles.CloseOpenHandlesToPathInProcess(path, processID);

If you study the code well, you will realize that the only specialty item here is that you need to terminate threads while you enumerate handles in order to stop deadlocks from happening. There is one special, odd, weird (whatever you want to call it) case in which deadlocks happen, and that is when you call NtQueryObject on handles which reference synchronous file objects (chances are that the file object was opened by a kernel-mode driver with FILE_SYNCHRONOUS_IO_NONALERT). The thread will wait indefinitely to acquire the file lock because interrupting the wait isn’t possible, which means you have to terminate the thread.

I recently set out to do some universal gravitation calculations in code, but I soon found that a lot of the existing or built-in data-types (Int64, Decimal, etc.) for doing so in .NET were rather inadequate (they either did not allow a high degree of precision, or they did not allow numbers large enough to suit my needs), so I searched for something that I could use to model very large numbers to an acceptably large degree of accuracy. That’s when I came across the BigRational class on CodePlex. This class decomposes large fractions into two BigInteger values (one to represent the numerator and another to represent the denominator), since any fractional number can be decomposed as such. I kept on royally butchering my by-hand calculations (since there are so many big numbers at play, along with unit conversions, etc.), and I got fed up to the point that I set out to create a code-based model in order to calculate surface gravities for the Sun and all of the planets in our Solar System using Newton’s law of universal gravitation:

using Numerics;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Threading.Tasks;

namespace UniversalPhysics
{

    public static class BigRationals
    {
        public static BigRational WithExponent(BigRational value, BigInteger exponent)
        {
            return BigRational.Multiply(value, BigRational.Pow(new BigRational(10, 1), exponent));
        }

        public static BigRational FromInteger(BigInteger value)
        {
            return new BigRational(value);
        }

        public static BigRational FromDouble(double value)
        {
            if (value == 0 || Double.IsNaN(value))
            {
                return new BigRational(0, 1);
            }
            if (Double.IsPositiveInfinity(value))
            {
                value = Double.MaxValue;
            }
            if (Double.IsNegativeInfinity(value))
            {
                value = Double.MinValue;
            }
            double fraction = value % 1;
            double numerator = value - fraction;
            double denominator = 1;
            // Notes:
            // 
            // - You are at the mercy of the precision of the double data type.
            // - If you debug this, you will see that the fraction variable changes in precision.
            // - The double data type does this to accomodate similar levels of precision.
            // - This may result in a slight skew of a very large value variable or a very small value variable.
            // - This effect is negligible when the value's precision is much less than Double.MaxValue's precision.
            while (!Double.IsNaN(fraction))
            {
                double decimalPlace = fraction * 10 * denominator - (fraction * 10 * denominator) % 1;
                if (Double.IsInfinity(numerator * 10 + decimalPlace))
                {
                    break;
                }
                if (Double.IsInfinity(denominator * 10))
                {
                    break;
                }
                denominator *= 10;
                numerator = numerator * 10 + decimalPlace;
                fraction = fraction - decimalPlace / denominator;
            }
            BigInteger numeratorAsBigInteger = new BigInteger(numerator);
            BigInteger denominatorAsBigInteger = new BigInteger(denominator);
            return new BigRational(numeratorAsBigInteger, denominatorAsBigInteger);
        }

        public static BigRational FromDoubleWithExponent(double value, BigInteger exponent)
        {
            return WithExponent(FromDouble(value), exponent);
        }
    }

    class Program
    {
        
        static SolarSystem System = new SolarSystem();

        static void Main(string[] args)
        {
            Console.WriteLine("Sun's Surface Gravity = " + (double)System.Sun.SurfaceGravity);
            Console.WriteLine("Mercury's Surface Gravity = " + (double)System.Mercury.SurfaceGravity);
            Console.WriteLine("Venus' Surface Gravity = " + (double)System.Venus.SurfaceGravity);
            Console.WriteLine("Earth's Surface Gravity = " + (double)System.Earth.SurfaceGravity);
            Console.WriteLine("Mars' Surface Gravity = " + (double)System.Mars.SurfaceGravity);
            Console.WriteLine("Jupiter's Surface Gravity = " + (double)System.Jupiter.SurfaceGravity);
            Console.WriteLine("Saturn's Surface Gravity = " + (double)System.Saturn.SurfaceGravity);
            Console.WriteLine("Uranus' Surface Gravity = " + (double)System.Uranus.SurfaceGravity);
            Console.WriteLine("Neptune's Surface Gravity = " + (double)System.Neptune.SurfaceGravity);
            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }
    }

    public class SolarSystem
    {

        public Planet Sun;
        public Planet Mercury;
        public Planet Venus;
        public Planet Earth;
        public Planet Mars;
        public Planet Jupiter;
        public Planet Saturn;
        public Planet Uranus;
        public Planet Neptune;

        public SolarSystem()
        {
            // Notes:
            //
            // - When viewed from above the Sun's north pole, the sun spins counter-clockwise on its axis.
            // - Prograde motion, when viewed from above the Sun's north pole, means counter-clockwise motion.
            // - Retrograde motion, when viewed from above the Sun's north pole, means clockwise motion.
            //
            // Putting this all together, when viewed from above the Sun's north pole:
            //
            // - The sun spins counter-clockwise.
            // - Venus and Uranus are the only two planets which have clockwise orbits.
            //      - All other planets have counter-clockwise orbits.
            // - Venus is the only planet that spins clockwise on its axis.
            //      - All other planets spin counter-clockwise on their axes.
            //      - Uranus kind-of also spins counter-clockwise, but the angle defined by its axial tilt makes it quite an oddball.
            //          - It doesn't spin like the other planets.
            //          - If you were the Sun, and a car in front of you was facing you with its front, and that car started to drive towards you, the way the wheels would spin on that car would be similar to the direction Uranus spins.
            //
            // What does this all mean?
            //
            // - Well, a planet's sidereal rotation period is really defined by axial tilt.
            // - Axial tilt (or obliquity), is the angle between an object's rotational axis and its orbital axis.
            //      - Equivalently, its the angle between a planet's equatorial plane and orbital plane.
            //      - It differs from orbital inclination.
            // - Don't take what I say for granted until you apply axial tilt for yourself, because I've made approximations with terms like clockwise and counter-clockwise.
            Sun = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(1.98855, 30),
                MeanRadius = BigRationals.FromInteger(696342000),
                SiderealRotationPeriod = TimeSpan.FromDays(25.05)
            };
            Mercury = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(3.3022, 23),
                MeanRadius = BigRationals.FromInteger(2439700),
                SiderealRotationPeriod = TimeSpan.FromHours(1407.5)
            };
            Venus = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(4.8676, 24),
                MeanRadius = BigRationals.FromInteger(6051800),
                SiderealRotationPeriod = TimeSpan.FromDays(243.0185) // Retrograde (this planet orbits the Sun in the opposite spin direction of the Sun).
            };
            Earth = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(5.97219, 24),
                MeanRadius = BigRationals.FromInteger(6371000),
                SiderealRotationPeriod = new TimeSpan(0, 23, 56, 4, 100)
            };
            Mars = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(6.4185, 23),
                MeanRadius = BigRationals.FromInteger(3389500),
                SiderealRotationPeriod = new TimeSpan(24, 37, 22)
            };
            Jupiter = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(1.8986, 27),
                MeanRadius = BigRationals.FromInteger(69911000),
                SiderealRotationPeriod = new TimeSpan(9, 55, 30)
            };
            Saturn = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(5.6846, 26),
                MeanRadius = BigRationals.FromInteger(58232000),
                SiderealRotationPeriod = new TimeSpan(10, 34, 0)
            };
            Uranus = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(8.681, 25),
                MeanRadius = BigRationals.FromInteger(25362000),
                SiderealRotationPeriod = new TimeSpan(17, 14, 24) // Retrograde (this planet orbits the Sun in the opposite spin direction of the Sun).
            };
            Neptune = new Planet
            {
                Mass = BigRationals.FromDoubleWithExponent(1.0243, 26),
                MeanRadius = BigRationals.FromInteger(24622000),
                SiderealRotationPeriod = new TimeSpan(16, 6, 36)
            };
        }
    }

    public class Planet
    {
        public BigRational Mass;
        public BigRational MeanRadius;
        public TimeSpan SiderealRotationPeriod;
        public BigRational AngularVelocity
        {
            get
            {
                return Laws.GetAngularVelocity(SiderealRotationPeriod);
            }
        }
        public BigRational SurfaceGravity
        {
            get
            {
                return Laws.GetNewtonianSurfaceGravity(Mass, MeanRadius);
            }
        }
    }

    public static class Laws
    {
        public static BigRational GetAngularVelocity(TimeSpan siderealRotationPeriod)
        {
            return BigRational.Divide(BigRational.Multiply(new BigRational(2.0), Constants.PI), BigRationals.FromDouble(siderealRotationPeriod.TotalSeconds));
        }

        public static BigRational GetNewtonianSurfaceGravity(BigRational mass, BigRational meanRadius)
        {
            return BigRational.Divide(BigRational.Multiply(Constants.GravitationalConstant, mass), BigRational.Pow(meanRadius, 2));
        }
    }

    public static class Constants
    {
        public static BigRational PI = BigRationals.FromDouble(3.141592654);
        public static BigRational GravitationalConstant = BigRationals.FromDoubleWithExponent(6.67384, -11);
        public static BigRational SpeedOfLight = BigRationals.FromInteger(299792458);
    }
}

Newton’s law of universal gravitation has been superseded by Einstein’s theory of general relativity, but it is still used as a good approximation of gravitational force. Relativity is for extreme precision, or for cases around the boundaries of Newton’s law of universal gravitation (very big masses, or very close massive objects). Alas, the output to all of that code above is as follows (the values obtained from Newton’s formulae are fairly close to the values from NASA’s Planetary Fact Sheet):

Sun's Surface Gravity = 273.695164677966
Mercury's Surface Gravity = 3.70259586050561
Venus' Surface Gravity = 8.86995750090755
Earth's Surface Gravity = 9.81960902526831
Mars' Surface Gravity = 3.72853358713613
Jupiter's Surface Gravity = 25.9249685707583
Saturn's Surface Gravity = 11.1879956428603
Uranus' Surface Gravity = 9.00696656052567
Neptune's Surface Gravity = 11.2760322511266
Press any key to exit.

The following code will always return -1.

"Example\\̼".IndexOf("Example\\");

This is because the Combining Seagull Below character, U+033C, is a combining character, and it will combine with the character previous to it in order to produce a new character. Using an ordinal string comparison would fix this problem for you. As an example, the following code will always return 0:

"Example\\̼".IndexOf("Example\\", StringComparison.OrdinalIgnoreCase)

The following code will always, also return -1.

"µ".IndexOf("μ");

This is because, although µ and μ are the same symbol, they are actually two different characters that are part of the Unicode character set (one is called the Micro Sign character, U+00B5, and the other is the Greek Small Letter Mu character, U+03BC). Using an ordinal string comparison will not fix this, but normalization will. The following code will always return 0:

"µ".Normalize(NormalizationForm.FormKD).IndexOf("μ".Normalize(NormalizationForm.FormKD))