问题:

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?

回答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;

}