I need to integrate IDX MLS into a real estate website. Also I want to know how to implement commercial and residential search?
You would use something like this:
https://www.nuget.org/packages/librets-dotnet/
Typically, a multiple listing service (MLS) uses a technology called RETS to serve listing data. In order to use RETS, you'll need to know the host/login URL the MLS provides and have an account with them for access. Then you can make calls to their RETS/IDX feed using the library above.
Here's the librets documentation: http://www.dis.com/NAR/libRETS_Dev_Guide.html
If I may, please let me provide more detail about these different acronyms:
MLS - Multiple Listing Service
IDX - Internet Data Exchange
RETS - Real Estate Transaction Standard