如何知道客户端PC上是否有PDF阅读器

Question

我需要知道是否有任何方法可以使用 VB6 检测客户端 PC (Windows) 中是否有任何 PDF 阅读器（Adobe Reader、Foxit Reader...）。 NET（C#）。

我无法通过读取Windows注册表来做到这一点，因为用户可能没有读取它的权限。

谢谢。

Answer 1

基于 Jerry Coffin 建议使用 FindExecutable 的示例（基于

Private Declare Function FindExecutable Lib "shell32.dll" _
  Alias "FindExecutableA"  ( _
  ByVal lpFile As String, _
  ByVal lpDirectory As String, _
  ByVal lpResult As String) As Long 

Private Declare Function lstrlen Lib "kernel32.dll" _
  Alias "lstrlenA" ( _
  ByVal lpString As Any) As Long

' FindExecutable Constants
Private Const ERROR_FILE_NOT_FOUND = 2&
Private Const ERROR_PATH_NOT_FOUND = 3&
Private Const ERROR_BAD_FORMAT = 11&

Private Sub Command1_Click()
  Dim Retval As Long, buffer As String

  ' init buffer 
  buffer = Space(256)

  Retval = FindExecutable("c:\windows\media\tada.wav", "", buffer)

  Select Case Retval
    Case 0
      Debug.Print "Not enough memory to execute this method." 
    Case 31
      Debug.Print "No file association found."
    Case ERROR_FILE_NOT_FOUND
      Debug.Print "File not found."
    Case ERROR_PATH_NOT_FOUND
      Debug.Print "Path not found."
    Case ERROR_BAD_FORMAT
      Debug.Print "The associated application is not a valid Win32 executable."
    Case Else
      Debug.Print "Associated application: " & Left$(buffer, lstrlen(buffer))
  End Select
End Sub

Answer 2

创建扩展名为“.pdf”的临时文件，然后使用 FindExectuable 作为您的临时文件。请注意，即使只有扩展名确实很重要，FindExecutable 仍然需要一个真实的文件，而不仅仅是具有正确扩展名的名称。

Answer 3

该 VB 例程将获取文件扩展名的默认可执行文件。如果没有可执行文件，则用户没有配置程序来处理扩展。

Private Declare Function FindExecutable Lib "shell32.dll" Alias "FindExecutableA" (ByVal lpFile As String, ByVal lpDirectory As String, ByVal lpResult As String) As Long

Function GetAssociation(ByVal Path As String, ByVal FileName As String) As String
   Dim Result As String
   Dim x As Long
   Dim lngLenBuff

   lngLenBuff = 256
   Result = String(lngLenBuff, vbNullChar)
   x = FindExecutable(FileName, Path, Result)
   GetAssociation = Left$(Result, InStr(Result, Chr$(0)) - 1) 'get string to left of the null'
End Function

Answer 4

我知道问题是针对 VB 的，但在 C# 中找到了 FindExecutable 的一个不错的实现 这里：

using System;
using System.Text;
using System.Runtime.InteropServices;

namespace PaytonByrd {
public class Win32API
{
  [DllImport("shell32.dll", EntryPoint="FindExecutable")] 
  public static extern long FindExecutableA(
    string lpFile, string lpDirectory, StringBuilder lpResult);

  public static string FindExecutable(
    string pv_strFilename)
  {
    StringBuilder objResultBuffer = 
      new StringBuilder(1024);
    long lngResult = 0;

    lngResult = 
      FindExecutableA(pv_strFilename, 
        string.Empty, objResultBuffer);

    if(lngResult >= 32)
    {
        return objResultBuffer.ToString();
    }

    return string.Format(
      "Error: ({0})", lngResult);
  }
}}

这是一个用法示例：

using System;
using System.Diagnostics;
using System.IO;
using PaytonByrd;

namespace CSharpFindExecutableTester
{
  class Class1
  {
    [STAThread]
    static void Main(string[] args)
    {
      foreach(string strFile in 
        Directory.GetFiles("c:\\"))
      {
        string strOutput = 
          string.Format(
            "{0} - Application: {1}",
            strFile, 
            Win32API.FindExecutable(
              strFile));

        Debug.WriteLine(strOutput);
      }
    }
  }
}