How to Open an XML file size of 700 MB using a C# language in Visual Studio ? And how can i validate the XMl (Without using XSD) if any tag is missing from that XML file ?

I have an XML file which is more than 700 MB in Size.

While opening any on the tools available to open that file, it says Disk size full or File is too large.

I want to write a program in C# windows application , which will help me help to open that big file.

I also want write a code which can validate any XML file , if any tag is missing from that file , it will tell me which tag is missing and on which line it is missing. I dont want to use XSD , because my XML files are different from each other.

Thanks!!