How to get EXE associated with a File Extension in the Registry

Introduction

This function returns the EXE filename and the command line for a submitted filename and filename extension. It uses the HKEY_CLASSES_ROOT registry hive to find the "shell open" program associated with a filename extension.

Using the code

Copy the GetRegisteredApplication function to your program.

Use the example below to show you how to call GetRegisteredApplication to retrieve the EXE associated with the filename extension and the shell commandline.

GetRegistryApplication Function

Imports Microsoft.Win32
Imports System.IO

...

Public Function GetRegisteredApplication( _
    ByVal ParamFileName As String, _
    ByVal FileExtension As String, _
    ByRef AppName As String, _
    ByRef ShellAppName As String) As Boolean
    '
    ' Return registered application based on the filename extension
    '
    Dim strExtension As String
    Dim strProgramName As String
    Dim strEXEFilename As String
    Dim regkey_HKEY_CLASSES_ROOT As RegistryKey ' HKEY_CLASSES_ROOT
    Dim regkey_ProgID As RegistryKey
    Dim regkey_OpenCommand As RegistryKey
    Dim intIndex As Integer

    Try
        ' Add starting dot to extension
        If FileExtension.StartsWith(".") Then
            strExtension = FileExtension
        Else
            strExtension = "." & FileExtension
        End If
        ' Get Programmatic Identifier for this extension
        Try
            regkey_HKEY_CLASSES_ROOT = Registry.ClassesRoot
            regkey_ProgID = regkey_HKEY_CLASSES_ROOT.OpenSubKey(strExtension)
            strProgramName = regkey_ProgID.GetValue(Nothing).ToString
            regkey_ProgID.Close()
        Catch
            ' Nothing found
            Return False
        End Try
        ' Get  application associated with the file extension
        Try
            regkey_OpenCommand = _
              regkey_HKEY_CLASSES_ROOT.OpenSubKey(strProgramName & "\shell\open\command")
            strEXEFilename = regkey_OpenCommand.GetValue(Nothing).ToString
            regkey_OpenCommand.Close()
        Catch
            ' No default application is registered
            Return False
        End Try
        intIndex = strEXEFilename.IndexOf(" %1")
        If intIndex > 0 Then
            ' Replace %1 placeholder with ParamFileName
            strEXEFilename = strEXEFilename.Substring(0, intIndex)
            AppName = strEXEFilename
            strEXEFilename = strEXEFilename & " " & _
               Convert.ToChar(34) & ParamFileName & Convert.ToChar(34)
            ShellAppName = strEXEFilename
        Else
            ' No %1 placeholder found, append ParamFileName
            AppName = strEXEFilename
            ShellAppName = strEXEFilename & " " & _
               Convert.ToChar(34) & ParamFileName & Convert.ToChar(34)
        End If
        Return True
    Catch ex As Exception
        Return False
    End Try
End Function

Dim strProgramName As String = ""
Dim strShellCommandLine As String = ""
Dim strTestFileName As String = "C:\windows\CSPU.txt"
If GetRegisteredApplication(strTestFileName, Path.GetExtension(strTestFileName), _
    strProgramName, strShellCommandLine) Then
    Console.WriteLine("Program Name: " & strProgramName & vbNewLine & _
        "Shell CommandLine: " & strShellCommandLine)
Else
    MsgBox("Association for " & strTestFileName & _
       " was not found.")
End If

Example Results

Program Name: C:\Windows\system32\NOTEPAD.EXE
Shell CommandLine: C:\Windows\system32\NOTEPAD.EXE "C:\windows\CSPU.txt"

History

Version 1: 5 September 2013.