Visual Studio C++ Dirty Files

Hi @Sid Kraft ,

Thank you for reaching out, and I’m sorry if the previous explanation wasn’t clear enough.

A file is considered “dirty” when it contains unsaved changes in memory. Even a small change, such as adding a comment, will mark the file as dirty. In Visual Studio, this is indicated by an asterisk (*) next to the file name, showing that there are changes that haven’t been saved yet.

Once you save the file, this mark will disappear. Visual Studio will also prompt you to save any unsaved changes before you close the application.

As we discussed earlier, if you have already saved the file (for example, by pressing Ctrl + S or using the Save button) but notice that the file reverts to its previous state afterward, I suggest checking the file’s last modified timestamp to better understand what might be happening. You may also want to refer back to your previous question for more details.

I completely understand your concern, and please be assured that I’ll do my best to help you resolve this issue. If my answer was helpful, you can follow this guidance to provide some feedback. This also help another find the solution easier.

In Visual Studio and the underlying APIs, a file or project is considered “dirty” when its in‑memory contents have changed since the last time it was loaded from disk or saved to disk.

More precisely:

• For text documents (such as C++ source files), ITextDocument.IsDirty indicates whether the associated ITextBuffer has changed since the file was last loaded or saved. If IsDirty is true, the buffer contents differ from what is on disk; if false, they are identical.
• For project files, properties such as Project.IsDirty indicate whether the project has changed and needs to be saved to disk.
• For other persisted objects (including projects and non-file items), IPersistFileFormat.IsDirty is used to determine whether the object has changed since being saved to its current file.

So, in general:

• Definition of a “dirty” file/object: Its in‑memory representation has been modified since the last successful load or save operation. The IDE or host uses the corresponding IsDirty/IsItemDirty checks to decide whether a Save is needed.
• What makes it dirty: Any edit that changes the underlying buffer or project state (typing in the editor, changing properties, adding/removing items, etc.) that the owning component records as a modification.
• How to make a file dirty: Perform an edit that changes its contents or metadata in the IDE (for example, type or delete a character in a C++ source file, change a project property, add/remove a file from the project). Once the component records that change, its IsDirty/IsItemDirty check will return true until it is saved.

If the Visual Studio project system or editor does not detect any such changes, the corresponding IsDirty checks will return false, and the environment will treat the file or project as clean and may skip saving it.

References:

• ITextDocument.IsDirty Property
• Project.IsDirty Property
• IPersistFileFormat.IsDirty(Int32) Method
• Project Persistence
• VCProject.IsDirty Property
• File Types Created for Visual Studio C++ Projects