Better way to check if a Path is a File or a Direc

Question

I am processing a TreeView of directories and files. A user can select either a file or a directory and then do something with it. This requires me to have a method which performs different actions based on the user's selection.

At the moment I am doing something like this to determine whether the path is a file or a directory:

bool bIsFile = false;
bool bIsDirectory = false;

try
{
    string[] subfolders = Directory.GetDirectories(strFilePath);

    bIsDirectory = true;
    bIsFile = false;
}
catch(System.IO.IOException)
{
    bIsFolder = false;
    bIsFile = true;
}

I cannot help to feel that there is a better way to do this! I was hoping to find a standard .NET method to handle this, but I haven't been able to do so. Does such a method exist, and if not, what is the most straightforward means to determine whether a path is a file or directory?

Answer 1

Here's what we use:

using System;

using System.IO;

namespace crmachine.CommonClasses
{

  public static class CRMPath
  {

    public static bool IsDirectory(string path)
    {
      if (path == null)
      {
        throw new ArgumentNullException("path");
      }

      string reason;
      if (!IsValidPathString(path, out reason))
      {
        throw new ArgumentException(reason);
      }

      if (!(Directory.Exists(path) || File.Exists(path)))
      {
        throw new InvalidOperationException(string.Format("Could not find a part of the path '{0}'",path));
      }

      return (new System.IO.FileInfo(path).Attributes & FileAttributes.Directory) == FileAttributes.Directory;
    } 

    public static bool IsValidPathString(string pathStringToTest, out string reasonForError)
    {
      reasonForError = "";
      if (string.IsNullOrWhiteSpace(pathStringToTest))
      {
        reasonForError = "Path is Null or Whitespace.";
        return false;
      }
      if (pathStringToTest.Length > CRMConst.MAXPATH) // MAXPATH == 260
      {
        reasonForError = "Length of path exceeds MAXPATH.";
        return false;
      }
      if (PathContainsInvalidCharacters(pathStringToTest))
      {
        reasonForError = "Path contains invalid path characters.";
        return false;
      }
      if (pathStringToTest == ":")
      {
        reasonForError = "Path consists of only a volume designator.";
        return false;
      }
      if (pathStringToTest[0] == ':')
      {
        reasonForError = "Path begins with a volume designator.";
        return false;
      }

      if (pathStringToTest.Contains(":") && pathStringToTest.IndexOf(':') != 1)
      {
        reasonForError = "Path contains a volume designator that is not part of a drive label.";
        return false;
      }
      return true;
    }

    public static bool PathContainsInvalidCharacters(string path)
    {
      if (path == null)
      {
        throw new ArgumentNullException("path");
      }

      bool containedInvalidCharacters = false;

      for (int i = 0; i < path.Length; i++)
      {
        int n = path[i];
        if (
            (n == 0x22) || // "
            (n == 0x3c) || // <
            (n == 0x3e) || // >
            (n == 0x7c) || // |
            (n  < 0x20)    // the control characters
          )
        {
          containedInvalidCharacters = true;
        }
      }

      return containedInvalidCharacters;
    }


    public static bool FilenameContainsInvalidCharacters(string filename)
    {
      if (filename == null)
      {
        throw new ArgumentNullException("filename");
      }

      bool containedInvalidCharacters = false;

      for (int i = 0; i < filename.Length; i++)
      {
        int n = filename[i];
        if (
            (n == 0x22) || // "
            (n == 0x3c) || // <
            (n == 0x3e) || // >
            (n == 0x7c) || // |
            (n == 0x3a) || // : 
            (n == 0x2a) || // * 
            (n == 0x3f) || // ? 
            (n == 0x5c) || // \ 
            (n == 0x2f) || // /
            (n  < 0x20)    // the control characters
          )
        {
          containedInvalidCharacters = true;
        }
      }

      return containedInvalidCharacters;
    }

  }

}