Names, extensions and parents

Read the parts of a path

FullPath file = FullPath.GetTempPath() / "reports" / "summary.tar.gz";

Assert.Equal("summary.tar.gz", file.Name);
Assert.Equal("summary.tar", file.NameWithoutExtension);
Assert.Equal(".gz", file.Extension);
Assert.Equal(FullPath.GetTempPath() / "reports", file.Parent);

Name, NameWithoutExtension and Extension return a string; Parent returns a FullPath. As the path has no trailing separator, the name of a folder is its last segment.

The parent of a root folder

A root folder, such as / or C:\, has no parent: Parent returns the empty path, where Path.GetDirectoryName returns null:

FullPath root = FullPath.FromPath(Path.GetPathRoot(Environment.CurrentDirectory)!);

// A root folder (/ or C:\) has no parent
Assert.True(root.Parent.IsEmpty);

A loop that walks up the folders stops when Parent.IsEmpty is true. To find the first folder that matches a condition, use the methods of Finding ancestors.

Change the extension or the name

FullPath file = FullPath.GetTempPath() / "reports" / "summary.tar.gz";

// Replace the last extension, all the extensions, or a number of them
Assert.Equal("summary.tar.zip", file.WithExtension(".zip").Name);
Assert.Equal("summary.zip", file.WithExtension(".zip", replaceAllTrailingExtensions: true).Name);
Assert.Equal("summary.zip", file.WithExtension("zip", extensionCount: 2).Name); // the leading dot is optional

// null removes the extension
Assert.Equal("summary.tar", file.WithExtension(null).Name);

// Rename the file and keep its folder
Assert.Equal(FullPath.GetTempPath() / "reports" / "readme.md", file.WithName("readme.md"));
Assert.Equal("details.gz", file.WithNameWithoutExtension("details").Name);

• WithExtension(extension) replaces the last extension, like Path.ChangeExtension. The leading dot of the new extension is optional, and null removes the extension.
• WithExtension(extension, replaceAllTrailingExtensions: true) replaces all the extensions, such as .tar.gz. WithExtension(extension, extensionCount) replaces the given number of extensions; the count must be greater than 0.
• WithName replaces the name and keeps the folder. WithNameWithoutExtension replaces the name and keeps the extension.
• These methods return a new path: they do not rename the file on disk. Pass both paths to File.Move to rename it.

Create the parent folder

CreateParentDirectory creates the folder that contains the path, and its own parents, when they do not exist. Call it before you create a file in a folder that may not exist yet. It does nothing on the empty path and on a root folder.