Difference between Interface and Abstract Class

Interface	Abstract Class
Interface is nothing but contract of the system which can be implemented on classes.	Abstract class is special kind of class that can not be instantiated but can be inherited.
A class may inherit several interfaces.	A class may inherit only one abstract class.
An interface cannot provide any code, just the signature.	An abstract class can provide signature as well as code to be overridden in the child classes.
Members of interface does not have any access modifier.	Members of abstract class have an access modifier.
An interface can not contain fields, constructor, destructor.	An abstract class can contain fields, constructor, destructor.
A class implementing an interface has to implement all the methods of the interface	A class implementing an abstract class does not need to implement all the methods of the abstract class
If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method.	If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly.
Reference can be created, it depends on child class object's memory.	Reference can not be created.

Difference between Value Type and Reference Type

Value Type	Reference Type
Value type they are stored on stack	Reference type they are stored on heap
When passed as value type new copy is created and passed so changes to variable does not get reflected back	When passed as Reference type then reference of that variable is passed so changes to variable does get reflected back
Value type store real data	Reference type store reference to the data.
Value types are faster in access	Reference types are slower in access.
Value type consists of primitive data types, structures, enumerations.	Reference type consists of class, array, interface, delegates
Value types derive from System.ValueType	Reference types derive from System.Object
Value types can not contain the value null.	Reference types can contain the value null.

Difference between Truncate and Delete Command in SQL

TRUNCATE	DELETE
TRUNCATE is a DDL command	DELETE is a DML command
TRUNCATE is executed using a table lock and whole table is locked for remove all records.	DELETE is executed using a row lock, each row in the table is locked for deletion.
We cannot use Where clause with TRUNCATE.	We can use where clause with DELETE to filter & delete specific records.
Minimal logging in transaction log, so it is performance wise faster.	It maintain the log, so it slower than TRUNCATE.
TRUNCATE TABLE removes the data by deallocating the data pages used to store the table data and records only the page deallocations in the transaction log.	The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row
Identify column is reset to its seed value if table contains any identity column.	Identity of column keep DELETE retain the identity
To use Truncate on a table you need at least ALTER permission on the table.	To use Delete you need DELETE permission on the table.
Truncate uses the less transaction space than Delete statement.	Delete uses the more transaction space than Truncate statement.
Truncate cannot be used with indexed views	Delete can be used with indexed views
TRUNCATE TABLE can’t activate a trigger because the operation does not log individual row deletions. When we run truncate command to remove all rows of table then it actually doesn’t removes any row, rather it deallocates the data pages. In case of Truncate triggers will not be fired because no modification takes place, we have just deallocated the data pages not deleted any row from table.	Delete activates a trigger because the operation are logged individually. When we execute Delete command, DELETE trigger will be initiated if present. Delete is a DML command and it deletes the data on row-by-row basis from a table. Which means delete is modifying the data by deleting it from the table. Triggers are fired when a DML statement executed on a table, so trigger will be fired in case of Delete command execution.