There could be many thousands interview questions on .net and few of them are asked in different companies. I can say that there are some core level questions that repeated in interviews and almost each company.
Generally about 10 questions are asked from different section of .net. and I am here to just summarizing them category/section wise. Hope it may be help you out to get your desired job.
1. CLR and CTS,CLS related question
o What are the important roles of CLR ? How CTS and CLS differ?
2. GC(Garbage Collector) related
o What is Garbage collector and how it works?
o What are the different phases in GC and how it works?
o How to force to run GC? What is managed code?
o When you use Window API, it is managed or unmanaged code?
3. Assembly related
o What is dll hell? What is Assembly and how a global assembly is created?
o How Assembly is differing from Namespace?
o Can we see Assembly?
o What is Manifest?
o How versioning is maintained?
o What is GAC and how it is maintained?
o What is Delay signing?
o What is Reflection?
o What is satellite assembly?
o What is NGEN.exe?
4. Value type and Reference type related
o What is Boxing/Unboxing?
o What are Value types and reference types?
o What is CodeDom?
o What is IUNKNOWN interface?
o Difference between Ref & out
5. Exception handling and Logging related
o Difference between System exception and Application exception?
o How to know the reason of exception being occurred for a particular user and what action you would to take to fix that.
6. Data handling and Controls related
o What is connection pooling
o What is different type of data controls
7. Life cycle and basics related
o HTTP Handler, Module
o Order of execution of Page_Load event in content page with master pages, user control pages.
o PostBack and Async PostBack and UpdatePanel
o Dynamic controls
o What are .pdb files
8. Authentication modes
o Different session management for not loosing state/session.
o How Security is maintained
9. Controls & Accessing controls values related
o How to access Html control values at server side(code behind)
o How to access User-control / Master page ‘s control from content page
o How to access Content page's control from Master page
o Difference between UserControl & CustomControl
10. Data transfer over pages related
o Different ways of transferring user data over pages
§ Client Level
§ Server Level
o Transferring control and their difference ( Server.Execute, Server.Transfer, Response.Redirect)
Best of Luck!!!:)