FileSystemInfo.Extension Property

Definition

Namespace:

System.IO

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

FileSystemInfo.cs

Gets the extension part of the file name, including the leading dot . even if it is the entire file name, or an empty string if no extension is present.

C#

public string Extension { get; }

Property Value

String

A string containing the FileSystemInfo extension.

Remarks

The Extension property returns the FileSystemInfo extension, which starts at, and includes, the last dot (.) in the file's full name. For example:

• For a file c:\NewFile.txt, this property returns ".txt".
• For a file c:\.gitignore, this property returns ".gitignore".
• For a file c:\noextension, this property returns an empty string "".
• For a file c:\a.b.c, this property returns ".c".
• When the FileInfo is constructed from a file path with a trailing dot, then that trailing dot is trimmed, so new FileInfo("foo.bar.").Extension returns ".bar".

The following table lists examples of other typical or related I/O tasks.

To do this...	See the example in this topic...
Create a text file.	How to: Write Text to a File
Write to a text file.	How to: Write Text to a File
Read from a text file.	How to: Read Text from a File
Retrieve the fully qualified path of a file.	GetFullPath
Retrieve only the file name a path.	GetFileNameWithoutExtension
Retrieve only the directory name from a path.	GetDirectoryName
Change the extension of a file.	ChangeExtension

Applies to

See also

• FileSystemWatcher
• File and Stream I/O
• How to: Read Text from a File
• How to: Write Text to a File