I am making a number of calls to IShellLinkW.GetPath(...) using PInvoke from C#. I would like to have these being executed concurrently on multiple async Tasks.
Are these calls thread safe? Can I do this?
Update:
What I am doing is resolving shortcuts as part of a larger task. Below is the code:
const uint STGM_READ = 0;
public static string ResolveShortcut(string filename)
{
ShellLink link = new ShellLink();
((IPersistFile)link).Load(filename, STGM_READ);
StringBuilder buff = new StringBuilder(260);
WIN32_FIND_DATAW data = new WIN32_FIND_DATAW();
IShellLinkW linkW = link as IShellLinkW;
linkW.GetPath(buff, buff.Capacity, out data, SLGP_FLAGS.SLGP_UNCPRIORITY);
return buff.ToString();
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
struct WIN32_FIND_DATAW
{
public uint dwFileAttributes;
public long ftCreationTime;
public long ftLastAccessTime;
public long ftLastWriteTime;
public uint nFileSizeHigh;
public uint nFileSizeLow;
public uint dwReserved0;
public uint dwReserved1;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string cFileName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
public string cAlternateFileName;
}
[ComImport(), InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
Guid("000214F9-0000-0000-C000-000000000046")]
{
/// <summary>Retrieves the path and file name of a Shell link object</summary>
void GetPath([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszFile, int cchMaxPath, out WIN32_FIND_DATAW pfd, SLGP_FLAGS fFlags);
/// <summary>Retrieves the list of item identifiers for a Shell link object</summary>
void GetIDList(out IntPtr ppidl);
/// <summary>Sets the pointer to an item identifier list (PIDL) for a Shell link object.</summary>
void SetIDList(IntPtr pidl);
/// <summary>Retrieves the description string for a Shell link object</summary>
void GetDescription([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszName, int cchMaxName);
/// <summary>Sets the description for a Shell link object. The description can be any application-defined string</summary>
void SetDescription([MarshalAs(UnmanagedType.LPWStr)] string pszName);
/// <summary>Retrieves the name of the working directory for a Shell link object</summary>
void GetWorkingDirectory([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszDir, int cchMaxPath);
/// <summary>Sets the name of the working directory for a Shell link object</summary>
void SetWorkingDirectory([MarshalAs(UnmanagedType.LPWStr)] string pszDir);
/// <summary>Retrieves the command-line arguments associated with a Shell link object</summary>
void GetArguments([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszArgs, int cchMaxPath);
/// <summary>Sets the command-line arguments for a Shell link object</summary>
void SetArguments([MarshalAs(UnmanagedType.LPWStr)] string pszArgs);
/// <summary>Retrieves the hot key for a Shell link object</summary>
void GetHotkey(out short pwHotkey);
/// <summary>Sets a hot key for a Shell link object</summary>
void SetHotkey(short wHotkey);
/// <summary>Retrieves the show command for a Shell link object</summary>
void GetShowCmd(out int piShowCmd);
/// <summary>Sets the show command for a Shell link object. The show command sets the initial show state of the window.</summary>
void SetShowCmd(int iShowCmd);
/// <summary>Retrieves the location (path and index) of the icon for a Shell link object</summary>
void GetIconLocation([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszIconPath,
int cchIconPath, out int piIcon);
/// <summary>Sets the location (path and index) of the icon for a Shell link object</summary>
void SetIconLocation([MarshalAs(UnmanagedType.LPWStr)] string pszIconPath, int iIcon);
/// <summary>Sets the relative path to the Shell link object</summary>
void SetRelativePath([MarshalAs(UnmanagedType.LPWStr)] string pszPathRel, int dwReserved);
/// <summary>Attempts to find the target of a Shell link, even if it has been moved or renamed</summary>
void Resolve(IntPtr hwnd, SLR_FLAGS fFlags);
/// <summary>Sets the path and file name of a Shell link object</summary>
void SetPath([MarshalAs(UnmanagedType.LPWStr)] string pszFile);
}
[ComImport, Guid("0000010b-0000-0000-C000-000000000046"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IPersistFile : IPersist
{
new void GetClassID(out Guid pClassID);
[PreserveSig]
int IsDirty();
[PreserveSig]
void Load([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName, uint dwMode);
[PreserveSig]
void Save([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName,
[In, MarshalAs(UnmanagedType.Bool)] bool fRemember);
[PreserveSig]
void SaveCompleted([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName);
[PreserveSig]
void GetCurFile([In, MarshalAs(UnmanagedType.LPWStr)] string ppszFileName);
}
You can have a look for yourself, COM servers register their threading requirements in the registry. IShellLinkW is implemented by the ShellLink coclass which has CLSID 00021401-0000-0000-C000-000000000046.
Start Regedit.exe and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID{00021401-0000-0000-C000-000000000046}\InProcServer32. You'll see:
ThreadingModel REG_SZ Both
"Both" means that you can use the interfaces implemented by ShellLinkW from a thread in the MTA as well.
So yes, it is okay.