In C#, how do you check if a path is virtual or not?

Question

Possible virtual paths:

/folder1/folder2/image.jpg
~/folder1/folder2/image.jpg
folder1/folder2/image.jpg

Concrete path:

C:\folder1\folder2\image.jpg
D:\folder1\folder2\image.jpg
C:/folder1/folder2/image.jpg
C:/folder1\folder2/image.jpg

How do you check whether a path is virtual or not in a way that's not prone to failure? The reason why I'm asking is because when I use Server.MapPath() on a concrete path, it will throw an exception. However, what I'm passing to Server.MapPath() can be any one of the examples I provided above and I don't know what it is before run-time.

Answer 1

This works well enough for me:

protected string GetPath(string path)
{
    if (Path.IsPathRooted(path))
    {
        return path;
    }

    return Server.MapPath(path);
}

Answer 2

Would Path.GetFullPath(string path) fit your needs? You could use that method then compare if the path changed.

if (path == Path.GetFullPath(path))
{
    // This is the full path (no changes)
}
else
{
    // This is not the full path i.e. 'virtual' (changes)
}

Reference: http://msdn.microsoft.com/en-us/library/system.io.path.getfullpath.aspx