How Do I...Enumerate directories and their contents?

VB Directory.exe [Run Sample] | [View Source]

The ability to look over files and subdirectories for a given directory is essential for many programming tasks. This QuickStart shows you how to use the FileInfo and DirectoryInfo classes. Why not the File and Directory classes? This QuickStart intends to display information such as the size, and creation date for a given file. In this case, it is easier to use FileInfo and DirectoryInfo objects. The File class focuses on the use of non-instantiated (static in C#, or shared in Visual Basic) methods, while the FileInfo class offers methods based on an instance of a FileInfo object. Directory and DirectoryInfo are similar.

The first task explains how create an instance of the DirectoryInfo object (based on the current directory), then find the fully-qualified path of that directory. Next, you can make a table of all the files and directories inside our current directory, so it will print the full path of the current directory at the top of that table. We use the GetFullPath method of the Path class to determine the fully-qualified path of our directory.

' don't forget your Imports statements at the top of your code...
Imports System
Imports System.IO
' ...

'  make an object which represents our current directory. The dot (".") represents this directory
Dim dir As DirectoryInfo = new DirectoryInfo(".")

'  make the header for our table, letting the user know the path we are in...
Console.WriteLine("Following is a listing for directory: {0}", Path.GetFullPath(dir.ToString()))

The objects inside the directory can be files or directories. You can iterate through the directory twice, looking for files first, and directories next. An alternate solution is to use the FileSystemInfo object, which can represent a FileInfo or a DirectoryInfo object. This means you only have to iterate through the collection once. Then, call the GetFileSystemInfos method of the object created in the code above, which returns an array of FileSystemInfo objects. You can iterate through that array with the foreach (For Each in Visual Basic), as the following code demonstrates.

Dim fsi As FileSystemInfo

'  loop through our array of FileSysteminfo objects
For Each fsi In dir.GetFileSystemInfos()

	'  ... the code in the following samples goes here.

Next fsi

So now you can see what kind of object each element of the FileSystemInfo array is, and process it accordingly. First test the instance of the FileSystemObject to see if it is a file. If it is, create a new instance of the FileInfo object to represent it. This enables you to call the methods particular to that kind of object. If you do not do this, you could not call properties such as Length, which does not exist in FileSystemInfo. In contrast, CreationTime is a property of the FileSystemInfo object, which is why you can deal with it before you enter your If statement, regardless of whether you have a file or a directory.

Notice that you are shortening the name you display to the user, primarily to save screen space. Because there can be file access or other related exceptions, execute this code in a Try block, to make sure it does not end abnormally. Put this code together with the code in the previous examples, and you have your program (once inside a method, of course). Note that this only demonstrates how to process a file.

Try
	Dim creationTime As DateTime = fsi.CreationTime
	Dim subLength As Integer = 25

        If (fsi is FileInfo) Then '  check to see if the current object is a file...

		Dim f As FileInfo = CType(fsi, FileInfo)

		'  this if statement simply ensures that we do not shorten the
		'  name of the file too much!
		if f.Name.Length < subLength Then
			subLength = f.Name.Length
		End If

		Dim name As string = f.Name.Substring(0, subLength)
                Dim size As long = f.Length

		'  format the output to the screen
       	        Console.WriteLine("{0, -25} {1,-12:N0} {2, -12} {3,-20:g}", _
				name, (size + " KB").PadLeft(12), "File", creationTime)

	Else   '  it must be a directory
		'  ...
	End If
Catch                  '  ignore!!! errors such as 'file being used' and so on...
End Try

Summary