VS Messages - IDE0090 - 'new' expression can be simplified

What is the difference between ExecuteScalar, ExecuteReader, and ExecuteNonQuery?

C# | ExecuteNonQuery

Can we inherit multiple classes?

No, multiple inheritances are not supported in .Net. 

How to add the prefix to the ID column with auto increment ID in SQL?

Here, I am taking an example of a Product. We have different types of  products, so I want to generate a new ProductId using a prefix of value like the below: