C# Signature:

[DllImport("shlwapi.dll")]
extern static int AssocCreate(
   ref Guid clsid,
   ref Guid riid,
   [MarshalAs(UnmanagedType.Interface)] out object ppv);

VB Signature:

Declare Function AssocCreate Lib "shlwapi.dll" (TODO) As TODO

User-Defined Types:

[Flags]
enum ASSOCF
{
   INIT_NOREMAPCLSID = 0x00000001,
   INIT_BYEXENAME = 0x00000002,
   OPEN_BYEXENAME = 0x00000002,
   INIT_DEFAULTTOSTAR = 0x00000004,
   INIT_DEFAULTTOFOLDER = 0x00000008,
   NOUSERSETTINGS = 0x00000010,
   NOTRUNCATE = 0x00000020,
   VERIFY = 0x00000040,
   REMAPRUNDLL = 0x00000080,
   NOFIXUPS = 0x00000100,
   IGNOREBASECLASS = 0x00000200,
   INIT_IGNOREUNKNOWN = 0x00000400
}

enum ASSOCSTR
{
   COMMAND = 1,
   EXECUTABLE,
   FRIENDLYDOCNAME,
   FRIENDLYAPPNAME,
   NOOPEN,
   SHELLNEWVALUE,
   DDECOMMAND,
   DDEIFEXEC,
   DDEAPPLICATION,
   DDETOPIC,
   INFOTIP,
   QUICKTIP,
   TILEINFO,
   CONTENTTYPE,
   DEFAULTICON,
   SHELLEXTENSION
}

enum ASSOCKEY
{
   SHELLEXECCLASS = 1,
   APP,
   CLASS,
   BASECLASS
}

enum ASSOCDATA
{
   MSIDESCRIPTOR = 1,
   NOACTIVATEHANDLER,
   QUERYCLASSSTORE,
   HASPERUSERASSOC,
   EDITFLAGS,
   VALUE
}

[Guid("c46ca590-3c3f-11d2-bee6-0000f805ca57"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IQueryAssociations
{
   void Init(
     [In] ASSOCF flags,
     [In, MarshalAs(UnmanagedType.LPWStr)] string pszAssoc,
     [In] UIntPtr hkProgid,
     [In] IntPtr hwnd);

   void GetString(
     [In] ASSOCF flags,
     [In] ASSOCSTR str,
     [In, MarshalAs(UnmanagedType.LPWStr)] string pwszExtra,
     [Out, MarshalAs(UnmanagedType.LPWStr)] StringBuilder pwszOut,
     [In, Out] ref int pcchOut);

   void GetKey(
     [In] ASSOCF flags,
     [In] ASSOCKEY str,
     [In, MarshalAs(UnmanagedType.LPWStr)] string pwszExtra,
     [Out] out UIntPtr phkeyOut);

   void GetData(
     [In] ASSOCF flags,
     [In] ASSOCDATA data,
     [In, MarshalAs(UnmanagedType.LPWStr)] string pwszExtra,
     [Out, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 4)] out byte[] pvOut,
     [In, Out] ref int pcbOut);

   void GetEnum(); // not used actually
}

static Guid CLSID_QueryAssociations = new Guid("a07034fd-6caa-4954-ac3f-97a27216f98a");
static Guid IID_IQueryAssociations = new Guid("c46ca590-3c3f-11d2-bee6-0000f805ca57");

Alternative Managed API:

Do you know one? Please contribute it!

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

try
{
   object obj;
   AssocCreate(
     ref CLSID_QueryAssociations,
     ref IID_IQueryAssociations,
     out obj);
   IQueryAssociations qa = (IQueryAssociations)obj;
   qa.Init(
     ASSOCF.INIT_DEFAULTTOSTAR,
     ".doc",
     UIntPtr.Zero, IntPtr.Zero);

   int size = 0;
   qa.GetString(ASSOCF.NOTRUNCATE, ASSOCSTR.COMMAND,
     "print", null, ref size);

   StringBuilder sb = new StringBuilder(size);
   qa.GetString(ASSOCF.NOTRUNCATE, ASSOCSTR.COMMAND,
     "print", sb, ref size);

   Console.WriteLine(".doc is printed by : {0}", sb.ToString());
}
catch(Exception e)
{
   if((uint)Marshal.GetHRForException(e) == 0x80070483)
     Console.WriteLine("No command line is associated to .doc print verb.");
   else
     throw;
}

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