DllImport如何确定CreateFileA和CreateFileW之间？

Question

当我使用P / Invoke来调用CreateFile时，

[DllImport("kernel32.dll")]
public static extern SafeFileHandle CreateFile(
    string lpFileName,
    uint dwDesiredAccess,
    uint dwShareMode,
    IntPtr SecurityAttributes,
    uint dwCreationDisposition,
    uint dwFlagsAndAttributes,
    IntPtr hTemplateFile
);

Windows如何决定调用CreateFileA或CreateFileW？