Desktop Functions:

   Smart Device Functions:

Show Recent Changes
Subscribe (RSS)
Misc. Pages
Helpful Tools
Suggested Reading
Website TODO List
Support Forum
Download Visual Studio Add-In

Terms of Use
Privacy Policy
AssocQueryString (shlwapi)

C# Signature:

[DllImport("Shlwapi.dll", SetLastError=true, CharSet = CharSet.Auto)]
static extern uint AssocQueryString(AssocF flags, AssocStr str, string pszAssoc, string pszExtra, [Out] StringBuilder pszOut, ref uint pcchOut);

VB Signature:

<DllImport("Shlwapi.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
Private Shared Function AssocQueryString(ByVal flags As UInteger, ByVal str As UInteger, ByVal pszAssoc As String, ByVal pszExtra As String, ByVal pszOut As Text.StringBuilder, ByRef pcchOut As UInteger) As UInteger
End Function

User-Defined Types:

enum AssocF : uint
    None = 0,
    Init_NoRemapCLSID = 0x1,
    Init_ByExeName = 0x2,
    Open_ByExeName = 0x2,
    Init_DefaultToStar = 0x4,
    Init_DefaultToFolder = 0x8,
    NoUserSettings = 0x10,
    NoTruncate = 0x20,
    Verify = 0x40,
    RemapRunDll = 0x80,
    NoFixUps = 0x100,
    IgnoreBaseClass = 0x200,
    Init_IgnoreUnknown = 0x400,
    Init_FixedProgId = 0x800,
    IsProtocol = 0x1000,
    InitForFile = 0x2000,

enum AssocStr
    Command = 1,

Alternative Managed API:

Do you know one? Please contribute it!


Also see (though this method is preferred, see

Tips & Tricks:

Please add some!

Sample Code:

static string AssocQueryString(AssocStr association, string extension)
  uint length = 0;
  uint ret = AssocQueryString(AssocF.None, association, extension, null, null, ref length);
  if (ret != 1) //expected S_FALSE
    throw new InvalidOperationException("Could not determine associated string");

  var sb = new StringBuilder((int)length); //(length-1) will probably work too as null termination is added
  ret = AssocQueryString(AssocF.None, association, extension, null, sb, ref length);
  if (ret != 0) //expected S_OK
    throw new InvalidOperationException("Could not determine associated string");

  return sb.ToString();


Please edit this page!

Do you have...

  • helpful tips or sample code to share for using this API in managed code?
  • corrections to the existing content?
  • variations of the signature you want to share?
  • additional languages you want to include?

Select "Edit This Page" on the right hand toolbar and edit it! Or add new pages containing supporting types needed for this API (structures, delegates, and more).

Access directly from VS:
Terms of Use
Edit This Page
Find References
Show Printable Version