He first asked to rate myself in OOP and in C#. Then he asked about some logical OOP concepts. Interface vs Abstract, Overriding if Polymorphism, Explicit and Implicit Interface implementation, Parent and Child object assignments, Boxing and Unboxing. In MVC, he asked about Viewbag and Model bindings, Best practices, patterns, singleton vs static classes, abstract factory, reflection, action filters, User authentication, custom attributes, page life cycle etc. In ADO.NET he asked about DataAdapter and DataReader, Mappings of sql data to model in a generic class.
A problem of counting occurrence of characters in a string was given.
In SQL, he asked about stored procedures vs functions, different types of tables, hash table etc.
.Net core page life cycle etc