C#/.NET: Change File Extension

You can just use the method Path.ChangeExtension from System.IO.

Let's have a look at a simple example:

string name_old = @"C:/MyFile.dat";
string name_new = Path.ChangeExtension(name_old, ".txt");

Here, we are changing the string "C:/MyFile.dat" to "C:/MyFile.txt".

However, this only changes the string and not a real file. If you also want to rename an existing file on your hard drive, you can afterwards use the function File.Move from System.IO. You can pass the old and the new file name including the path to this function:

File.Move(name_old, name_new);

Note: When passing a string without file extension to Path.ChangeExtension, the file extension is just appended to the string.
Last update on 2024-01-01 | Created on 2014-09-04