Top 74 C# Interview Questions

C# is a strongly-typed language. It means any variable that we define must have a type such as integer, float, decimal, text, etc.

C# mainly categorized data types in two types:

• Value types
• Reference types

Value types include simple types (such as int, float, bool, and char), enum types, struct types, and Nullable value types.

Reference types include class types, interface types, delegate types, and array types.

In C#, these data types are categorized based on how they store their value in the memory.

Value Type

A data type is a value type if it holds a data value within its own memory space. It means the variables of these data types directly contain values.

• Fixed memory size
• Stored in Stack memory
• Holds actual value
• i.e. int, char, bool, etc.

Reference types

Unlike value types, a reference type doesn't store its value directly. Instead, it stores the address where the value is being stored.

• Not fixed memory
• Stored in Heap memory
• Holds memory address of actual value
• i.e. string, array, class, etc.

Good to know

• Value types are stored wherever they are declared. For example, an int's value inside a function as a local variable would be stored on the stack, whilst an int's value declared as member in a class would be stored on the heap with the class it is declared in.
• When a reference type variable is declared, it contains the value null until an object that has been created using the keywords new is assigned to it.

The finally block will execute when the try/catch block leaves the execution, no matter what condition cause it. It always executes whether the try block terminates normally or terminates due to an exception. The main purpose of finally block is to release the system resources.

Conditions of leaving try/catch block could be anything including execution of a break, continue, goto, or return statement, or propagation of an exception out of the try statement.

Yes, a finally block always executes, regardless of whether an exception is thrown.

Yes, the finally block is executed however the flow leaves the try block - whether by reaching the end, returning, or throwing an exception.

throw preserves the stack trace while throw ex does not.

If you use throw ex, original stack trace will be wiped out completely and you will be left with only the stack trace from where you threw the exception. Hence It's recommended to use throw instead of throw ex.

Explain Gen0, Gen1, Gen2 here, also Stack vs Heap.

Explain Dispose() vs Finalize()