Question

I want to determine if a folder contains a file, when both are specified by a path.

At first glance this seems simple. Just check if the file path starts with the directory path. However, this naive check ignores several issues:

• Paths may be relative or absolute
• Paths may use the alternate directory separator
• Paths may use inconsistent casing, which matters depending on the OS
• Different paths may refer to the same location
• Probably some more that I don’t know about

Is there an existing method in the framework, or do I have to write my own?

Answer 1

As far as I know, there is no built-in .NET method to do this, but the following function should accomplish this using the FileInfo and DirectoryInfo classes:

public static bool FolderContainsFile(String folder, String file)
{
    //Create FileInfo and DirectoryInfo objects
    FileInfo fileInfo = new FileInfo(file);
    DirectoryInfo dirInfo = new DirectoryInfo(folder);

    DirectoryInfo currentDirectory = fileInfo.Directory;
    if (dirInfo.Equals(currentDirectory))
        return true;

    while (currentDirectory.Parent != null)
    {
        currentDirectory = currentDirectory.Parent;

        if(currentDirectory.Equals(dirInfo)
            return true;
    }

    return false;

}