C # solve PathTooLongException by overwriting the entire System. IO

Recently, because the company's file management system needs to support long file names, that is, the limit of 260 characters, the company found relevant information online and found a dll written by a foreign cool man, based on the original author, we have added some of the methods we need to implement. The method is as follows:

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public static DirectorySecurity GetDirectorySecurity(string longname)        {            int length = 0;            byte[] buffer;// = new byte[65536];            bool ret = Win32Interop.GetFileSecurity(longname, (int)(SECURITY_INFORMATION.OWNER_SECURITY_INFORMATION | SECURITY_INFORMATION.GROUP_SECURITY_INFORMATION ), null, 0, out length);            if (length > 0)            {                buffer = new byte[length];                ret = Win32Interop.GetFileSecurity(longname, (int)(SECURITY_INFORMATION.OWNER_SECURITY_INFORMATION | SECURITY_INFORMATION.GROUP_SECURITY_INFORMATION), buffer, (uint)length, out length);                DirectorySecurity pSD = new DirectorySecurity();                pSD.SetSecurityDescriptorBinaryForm(buffer);                return pSD;            }            else            {                return null;            }        }        public static DirectorySecurity GetDirectorySecurity(string longname, AccessControlSections sec)        {            int length = 0;            byte[] buffer;// = new byte[65536];            bool ret = Win32Interop.GetFileSecurity(longname, (int)sec, null, 0, out length);            if (length > 0)            {                buffer = new byte[length];                ret = Win32Interop.GetFileSecurity(longname, (int)sec, buffer, (uint)length, out length);                DirectorySecurity pSD = new DirectorySecurity();                pSD.SetSecurityDescriptorBinaryForm(buffer);                return pSD;            }            else            {                return null;            }        }        public static FileSecurity GetFileSecurity(string longname)        {            int length = 0;            byte[] buffer;// = new byte[65536];            bool ret = Win32Interop.GetFileSecurity(longname, (int)(SECURITY_INFORMATION.OWNER_SECURITY_INFORMATION | SECURITY_INFORMATION.GROUP_SECURITY_INFORMATION), null, 0, out length);            if (length > 0)            {                buffer = new byte[length];                ret = Win32Interop.GetFileSecurity(longname, (int)(SECURITY_INFORMATION.OWNER_SECURITY_INFORMATION | SECURITY_INFORMATION.GROUP_SECURITY_INFORMATION), buffer, (uint)length, out length);                FileSecurity pSD = new FileSecurity();                pSD.SetSecurityDescriptorBinaryForm(buffer);                return pSD;            }            else            {                return null;            }        }        public static FileSecurity GetFileSecurity(string longname,AccessControlSections sec)        {            int length = 0;            byte[] buffer;// = new byte[65536];            bool ret = Win32Interop.GetFileSecurity(longname, (int)sec, null, 0, out length);            if (length > 0)            {                buffer = new byte[length];                ret = Win32Interop.GetFileSecurity(longname, (int)sec, buffer, (uint)length, out length);                FileSecurity pSD = new FileSecurity();                pSD.SetSecurityDescriptorBinaryForm(buffer);                return pSD;            }            else            {                return null;            }        }