Extension Property

FileSystemInfo.Extension Property


Gets the string representing the extension part of the file.

Namespace:   System.IO
Assembly:  mscorlib (in mscorlib.dll)

public string Extension { get; }

Property Value

Type: System.String

A string containing the FileSystemInfo extension.

The Extension property returns the FileSystemInfo extension, including the period (.). For example, for a file c:\NewFile.txt, this property returns ".txt".

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.


Retrieve only the file name a path.


Retrieve only the directory name from a path.


Change the extension of a file.


Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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