You can prevent a class from overriding in C# by using the sealed keyword; whereas, the NotInheritable keyword is used to prevent a class from overriding in Visual Basic.

When a class is derived from another class, then the members of the base class become the members of the derived class. The access modifier used while accessing members of the base class specifies the access status of the base class members inside the derived class.

The syntax to inherit a class from another class in C# is as follows:
class MyNewClass : MyBaseclass

.NET does not support multiple inheritance directly because in .NET, a class cannot inherit from more than one class. .NET supports multiple inheritance through interfaces.

The System.Collections namespace contains all the collection classes.

The JIT compiler is an important element of CLR, which loads MSIL on target machines for execution. The MSIL is stored in .NET assemblies after the developer has compiled the code written in any .NET-compliant programming language, such as Visual Basic and C#.

JIT compiler translates the MSIL code of an assembly and uses the CPU architecture of the target machine to execute a .NET application. It also stores the resulting native code so that it is accessible for subsequent calls. If a code executing on a target machine calls a non-native method, the JIT compiler converts the MSIL of that method into native code. JIT compiler also enforces type-safety in runtime environment of .NET Framework. It checks for the values that are passed to parameters of any method.

For example, the JIT compiler detects any event, if a user tries to assign a 32-bit value to a parameter that can only accept 8-bit value.

To be able to display the output directly to the browser, we have to use the special tags <?= and ?>.

The mysqli extension , or as it is sometimes known, the MYSQL improved extension ,was developed to take advantage of new features found in MYSQL systems versions 4.1.3 and later.

The mysqli extension has a number of benfits,the key enhancements over the mysql extension being:
=> Object-oriented interface
=> Support for prepared statements
=> Support for multiple statements
=> Support for transactions
=> Enhanced debugging capabilities
=> Embedded server support

unlink()-deletes the given file from the file system.
unset() -makes a variable undefined.