I know how to create a symbolic link in windows in a .bat script:
mklink /J <LinkPath> <OriginalResourcePath>
How to do the same thing in C# ?
I've not been happy with the googling, because i'm a beginner in C# and I probably don't use the right terms. Anybody can indicate the API to use please ?
Warning: The question is not clear as it refers to symbolic links but at the same time refers to the /J switch that is used to create a junction. This answer refers to "how to create a symbolic link in c#" (without the /J). Instead, For creating junctions, please refer to In .NET, how do I Create a Junction in NTFS, as opposed to a Symlink?.
This is how symbolic links can be created:
using System.Runtime.InteropServices;
using System.IO;
namespace ConsoleApplication
{
class Program
{
[DllImport("kernel32.dll")]
static extern bool CreateSymbolicLink(
string lpSymlinkFileName, string lpTargetFileName, SymbolicLink dwFlags);
enum SymbolicLink
{
File = 0,
Directory = 1
}
static void Main(string[] args)
{
string symbolicLink = @"c:\bar.txt";
string fileName = @"c:\temp\foo.txt";
using (var writer = File.CreateText(fileName))
{
writer.WriteLine("Hello World");
}
CreateSymbolicLink(symbolicLink, fileName, SymbolicLink.File);
}
}
}
This will create a symbolic link file called bar.txt on the C:-drive which links to the foo.txt text file stored in the C:\temp directory.
mklink /J creates a (directory) junction. CreateSymbolicLink creates a symbolic link (to a file or directory). I think the real answer is here. Or the question was "inaccurate", since the OP accepted this answer. –
Gladine Here is a project that has the PInvoke signatures for creating junctions: http://www.codeproject.com/Articles/15633/Manipulating-NTFS-Junction-Points-in-NET. The code is copied below:
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using Microsoft.Win32.SafeHandles;
namespace Util {
/// <summary>
/// Provides access to NTFS junction points in .Net.
/// </summary>
public static class JunctionPoint {
/// <summary>
/// The file or directory is not a reparse point.
/// </summary>
private const int ERROR_NOT_A_REPARSE_POINT = 4390;
/// <summary>
/// The reparse point attribute cannot be set because it conflicts with an existing attribute.
/// </summary>
private const int ERROR_REPARSE_ATTRIBUTE_CONFLICT = 4391;
/// <summary>
/// The data present in the reparse point buffer is invalid.
/// </summary>
private const int ERROR_INVALID_REPARSE_DATA = 4392;
/// <summary>
/// The tag present in the reparse point buffer is invalid.
/// </summary>
private const int ERROR_REPARSE_TAG_INVALID = 4393;
/// <summary>
/// There is a mismatch between the tag specified in the request and the tag present in the reparse point.
/// </summary>
private const int ERROR_REPARSE_TAG_MISMATCH = 4394;
/// <summary>
/// Command to set the reparse point data block.
/// </summary>
private const int FSCTL_SET_REPARSE_POINT = 0x000900A4;
/// <summary>
/// Command to get the reparse point data block.
/// </summary>
private const int FSCTL_GET_REPARSE_POINT = 0x000900A8;
/// <summary>
/// Command to delete the reparse point data base.
/// </summary>
private const int FSCTL_DELETE_REPARSE_POINT = 0x000900AC;
/// <summary>
/// Reparse point tag used to identify mount points and junction points.
/// </summary>
private const uint IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003;
/// <summary>
/// This prefix indicates to NTFS that the path is to be treated as a non-interpreted
/// path in the virtual file system.
/// </summary>
private const string NonInterpretedPathPrefix = @"\??\";
[Flags]
private enum EFileAccess : uint {
GenericRead = 0x80000000,
GenericWrite = 0x40000000,
GenericExecute = 0x20000000,
GenericAll = 0x10000000,
}
[Flags]
private enum EFileShare : uint {
None = 0x00000000,
Read = 0x00000001,
Write = 0x00000002,
Delete = 0x00000004,
}
private enum ECreationDisposition : uint {
New = 1,
CreateAlways = 2,
OpenExisting = 3,
OpenAlways = 4,
TruncateExisting = 5,
}
[Flags]
private enum EFileAttributes : uint {
Readonly = 0x00000001,
Hidden = 0x00000002,
System = 0x00000004,
Directory = 0x00000010,
Archive = 0x00000020,
Device = 0x00000040,
Normal = 0x00000080,
Temporary = 0x00000100,
SparseFile = 0x00000200,
ReparsePoint = 0x00000400,
Compressed = 0x00000800,
Offline = 0x00001000,
NotContentIndexed = 0x00002000,
Encrypted = 0x00004000,
Write_Through = 0x80000000,
Overlapped = 0x40000000,
NoBuffering = 0x20000000,
RandomAccess = 0x10000000,
SequentialScan = 0x08000000,
DeleteOnClose = 0x04000000,
BackupSemantics = 0x02000000,
PosixSemantics = 0x01000000,
OpenReparsePoint = 0x00200000,
OpenNoRecall = 0x00100000,
FirstPipeInstance = 0x00080000
}
[StructLayout(LayoutKind.Sequential)]
private struct REPARSE_DATA_BUFFER {
/// <summary>
/// Reparse point tag. Must be a Microsoft reparse point tag.
/// </summary>
public uint ReparseTag;
/// <summary>
/// Size, in bytes, of the data after the Reserved member. This can be calculated by:
/// (4 * sizeof(ushort)) + SubstituteNameLength + PrintNameLength +
/// (namesAreNullTerminated ? 2 * sizeof(char) : 0);
/// </summary>
public ushort ReparseDataLength;
/// <summary>
/// Reserved; do not use.
/// </summary>
public ushort Reserved;
/// <summary>
/// Offset, in bytes, of the substitute name string in the PathBuffer array.
/// </summary>
public ushort SubstituteNameOffset;
/// <summary>
/// Length, in bytes, of the substitute name string. If this string is null-terminated,
/// SubstituteNameLength does not include space for the null character.
/// </summary>
public ushort SubstituteNameLength;
/// <summary>
/// Offset, in bytes, of the print name string in the PathBuffer array.
/// </summary>
public ushort PrintNameOffset;
/// <summary>
/// Length, in bytes, of the print name string. If this string is null-terminated,
/// PrintNameLength does not include space for the null character.
/// </summary>
public ushort PrintNameLength;
/// <summary>
/// A buffer containing the unicode-encoded path string. The path string contains
/// the substitute name string and print name string.
/// </summary>
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x3FF0)]
public byte[] PathBuffer;
}
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool DeviceIoControl(IntPtr hDevice, uint dwIoControlCode,
IntPtr InBuffer, int nInBufferSize,
IntPtr OutBuffer, int nOutBufferSize,
out int pBytesReturned, IntPtr lpOverlapped);
[DllImport("kernel32.dll", SetLastError = true)]
private static extern IntPtr CreateFile(
string lpFileName,
EFileAccess dwDesiredAccess,
EFileShare dwShareMode,
IntPtr lpSecurityAttributes,
ECreationDisposition dwCreationDisposition,
EFileAttributes dwFlagsAndAttributes,
IntPtr hTemplateFile);
/// <summary>
/// Creates a junction point from the specified directory to the specified target directory.
/// </summary>
/// <remarks>
/// Only works on NTFS.
/// </remarks>
/// <param name="targetDir">The target directory to create</param>
/// <param name="sourceDir">The source directory to alias</param>
/// <param name="overwrite">If true overwrites an existing reparse point or empty directory</param>
/// <exception cref="IOException">Thrown when the junction point could not be created or when
/// an existing directory was found and <paramref name="overwrite" /> if false</exception>
public static void Create(string sourceDir, string targetDir, bool overwrite) {
sourceDir = Path.GetFullPath(sourceDir);
if (!Directory.Exists(sourceDir))
throw new IOException($"Source path does not exist or is not a directory.");
if (Directory.Exists(targetDir))
throw new IOException($"Directory '{targetDir}' already exists.");
Directory.CreateDirectory(targetDir);
using (SafeFileHandle handle = OpenReparsePoint(targetDir, EFileAccess.GenericWrite)) {
byte[] sourceDirBytes = Encoding.Unicode.GetBytes(NonInterpretedPathPrefix + Path.GetFullPath(sourceDir));
REPARSE_DATA_BUFFER reparseDataBuffer = new REPARSE_DATA_BUFFER();
reparseDataBuffer.ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
reparseDataBuffer.ReparseDataLength = (ushort)(sourceDirBytes.Length + 12);
reparseDataBuffer.SubstituteNameOffset = 0;
reparseDataBuffer.SubstituteNameLength = (ushort)sourceDirBytes.Length;
reparseDataBuffer.PrintNameOffset = (ushort)(sourceDirBytes.Length + 2);
reparseDataBuffer.PrintNameLength = 0;
reparseDataBuffer.PathBuffer = new byte[0x3ff0];
Array.Copy(sourceDirBytes, reparseDataBuffer.PathBuffer, sourceDirBytes.Length);
int inBufferSize = Marshal.SizeOf(reparseDataBuffer);
IntPtr inBuffer = Marshal.AllocHGlobal(inBufferSize);
try {
Marshal.StructureToPtr(reparseDataBuffer, inBuffer, false);
int bytesReturned;
bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_SET_REPARSE_POINT,
inBuffer, sourceDirBytes.Length + 20, IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);
if (!result)
ThrowLastWin32Error($"Unable to create junction point '{sourceDir}' -> '{targetDir}'.");
} finally {
Marshal.FreeHGlobal(inBuffer);
}
}
}
/// <summary>
/// Deletes a junction point at the specified source directory along with the directory itself.
/// Does nothing if the junction point does not exist.
/// </summary>
/// <remarks>
/// Only works on NTFS.
/// </remarks>
/// <param name="junctionPoint">The junction point path</param>
public static void Delete(string junctionPoint) {
if (!Directory.Exists(junctionPoint)) {
if (File.Exists(junctionPoint))
throw new IOException("Path is not a junction point.");
return;
}
using (SafeFileHandle handle = OpenReparsePoint(junctionPoint, EFileAccess.GenericWrite)) {
REPARSE_DATA_BUFFER reparseDataBuffer = new REPARSE_DATA_BUFFER();
reparseDataBuffer.ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
reparseDataBuffer.ReparseDataLength = 0;
reparseDataBuffer.PathBuffer = new byte[0x3ff0];
int inBufferSize = Marshal.SizeOf(reparseDataBuffer);
IntPtr inBuffer = Marshal.AllocHGlobal(inBufferSize);
try {
Marshal.StructureToPtr(reparseDataBuffer, inBuffer, false);
int bytesReturned;
bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_DELETE_REPARSE_POINT,
inBuffer, 8, IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);
if (!result)
ThrowLastWin32Error("Unable to delete junction point.");
} finally {
Marshal.FreeHGlobal(inBuffer);
}
try {
Directory.Delete(junctionPoint);
} catch (IOException ex) {
throw new IOException("Unable to delete junction point.", ex);
}
}
}
/// <summary>
/// Determines whether the specified path exists and refers to a junction point.
/// </summary>
/// <param name="path">The junction point path</param>
/// <returns>True if the specified path represents a junction point</returns>
/// <exception cref="IOException">Thrown if the specified path is invalid
/// or some other error occurs</exception>
public static bool Exists(string path) {
if (!Directory.Exists(path))
return false;
using (SafeFileHandle handle = OpenReparsePoint(path, EFileAccess.GenericRead)) {
string target = InternalGetTarget(handle);
return target != null;
}
}
/// <summary>
/// Gets the target of the specified junction point.
/// </summary>
/// <remarks>
/// Only works on NTFS.
/// </remarks>
/// <param name="junctionPoint">The junction point path</param>
/// <returns>The target of the junction point</returns>
/// <exception cref="IOException">Thrown when the specified path does not
/// exist, is invalid, is not a junction point, or some other error occurs</exception>
public static string GetTarget(string junctionPoint) {
using (SafeFileHandle handle = OpenReparsePoint(junctionPoint, EFileAccess.GenericRead)) {
string target = InternalGetTarget(handle);
if (target == null)
throw new IOException("Path is not a junction point.");
return target;
}
}
private static string InternalGetTarget(SafeFileHandle handle) {
int outBufferSize = Marshal.SizeOf(typeof(REPARSE_DATA_BUFFER));
IntPtr outBuffer = Marshal.AllocHGlobal(outBufferSize);
try {
int bytesReturned;
bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_GET_REPARSE_POINT,
IntPtr.Zero, 0, outBuffer, outBufferSize, out bytesReturned, IntPtr.Zero);
if (!result) {
int error = Marshal.GetLastWin32Error();
if (error == ERROR_NOT_A_REPARSE_POINT)
return null;
ThrowLastWin32Error("Unable to get information about junction point.");
}
REPARSE_DATA_BUFFER reparseDataBuffer = (REPARSE_DATA_BUFFER)
Marshal.PtrToStructure(outBuffer, typeof(REPARSE_DATA_BUFFER));
if (reparseDataBuffer.ReparseTag != IO_REPARSE_TAG_MOUNT_POINT)
return null;
string targetDir = Encoding.Unicode.GetString(reparseDataBuffer.PathBuffer,
reparseDataBuffer.SubstituteNameOffset, reparseDataBuffer.SubstituteNameLength);
if (targetDir.StartsWith(NonInterpretedPathPrefix))
targetDir = targetDir.Substring(NonInterpretedPathPrefix.Length);
return targetDir;
} finally {
Marshal.FreeHGlobal(outBuffer);
}
}
private static SafeFileHandle OpenReparsePoint(string reparsePoint, EFileAccess accessMode) {
SafeFileHandle reparsePointHandle = new SafeFileHandle(CreateFile(reparsePoint, accessMode,
EFileShare.Read | EFileShare.Write | EFileShare.Delete,
IntPtr.Zero, ECreationDisposition.OpenExisting,
EFileAttributes.BackupSemantics | EFileAttributes.OpenReparsePoint, IntPtr.Zero), true);
if (Marshal.GetLastWin32Error() != 0)
ThrowLastWin32Error("Unable to open reparse point.");
return reparsePointHandle;
}
private static void ThrowLastWin32Error(string message) {
throw new IOException(message, Marshal.GetExceptionForHR(Marshal.GetHRForLastWin32Error()));
}
}
}
For anyone using .NET 6 or greater this has been simplified a great deal and is now part of the framework.
using System.IO;
private void MyMethod(string source, string target)
{
// Create symbolic link for directory (answers this question)
Directory.CreateSymbolicLink(source, target);
// Create symbolic link for file (additional reference)
File.CreateSymbolicLink(source, target);
}
File.CreateSymbolicLink –
Laissezfaire Another way it to use mklink. It turns out that mklink is an internal command so you need cmd.exe to call it:
var psi=new ProcessStartInfo("cmd.exe"," /C mklink \""+link_name+"\" \""+ target_name + "\"");
psi.CreateNoWindow = true;
psi.UseShellExecute = false;
Process.Start(psi).WaitForExit();
You can add /J or /d etc as you need.
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/Jswitch tomklink)? From the accepted answer it looks you were actually looking for a symbolic link instead (invokemklinkwithout any option). – Gladine