Validation controls are responsible to validate the data of an input control. Whenever you provide any input to an application, it performs the validation and displays an error message to user, in case the validation fails.

ASP.NET 4.0 contains the following six types of validation controls:

   => CompareValidator - Performs a comparison between the values contained in two controls.
   => CustomValidator - Writes your own method to perform extra validation.
   => RangeValidator- Checks value according to the range of value.
   => RegularExpressionValidator - Ensures that input is according to the specified pattern or not.
   =>  RequiredFieldValidator - Checks either a control is empty or not.
   => ValidationSummary - Displays a summary of all validation error in a central location.

The code-behind feature of ASP.NET enables you to divide an ASP.NET page into two files - one consisting of the presentation data, and the second, which is also called the code-behind file, consisting of all the business logic. The presentation data contains the interface elements, such as HTML controls and Web server controls, and the code-behind contains the event-handling process to handle the events that are fired by these controls. The file that contains the presentation data has the .aspx extension. The code behind file has either the .cs extension (if you are using the programming language C#) or the .vb (if you are using the programming language Visual Basic .NET) extension.

The basic difference between ASP and ASP.NET is that ASP is interpreted; whereas, ASP.NET is compiled. This implies that since ASP uses VBScript; therefore, when an ASP page is executed, it is interpreted. On the other hand, ASP.NET uses .NET languages, such as C# and VB.NET, which are compiled to Microsoft Intermediate Language (MSIL).

ASP.NET is a specification developed by Microsoft to create dynamic Web applications, Web sites, and Web services. It is a part of .NET Framework. You can create ASP.NET applications in most of the .NET compatible languages, such as Visual Basic, C#, and J#. The ASP.NET compiles the Web pages and provides much better performance than scripting languages, such as VBScript. The Web Forms support to create powerful forms-based Web pages. You can use ASP.NET Web server controls to create interactive Web applications. With the help of Web server controls, you can easily create a Web application.

DLR is a runtime environment that allows you to integrate dynamic languages with the Common Language Runtime (CLR) by adding a set of services, such as expression trees, call site caching, and dynamic object interoperability to the CLR.

The System.Dynamic and System.Runtime.CompilerServices namespaces are used to hold the classes for DLR. It also provides dynamic features to statically-typed languages, such as C# and Visual Basic to enable their interoperation with dynamic languages.

The following are the usages of the Command object in AD0.NET:

The Command object in AD0.NET executes a command against the database and retrieves a DataReader or DataSet object.

  =>  It also executes the INSERT, UPDATE, or DELETE command against the database.
  =>  All the command objects are derived from the DbCommand class.
  =>  The command object is represented by two classes: SqlCommand and OleDbCommand.
  =>  The Command object provides three methods to execute commands on the database:
  =>  The ExecuteNonQuery() method executes the commands and does not return any value.
  =>  The ExecuteScalar() method returns a single value from a database query.
  =>  The ExecuteReader() method returns a result set by using the DataReader object.

The following are the usages of the Command object in AD0.NET:

The Command object in AD0.NET executes a command against the database and retrieves a DataReader or DataSet object.

  =>  It also executes the INSERT, UPDATE, or DELETE command against the database.
  =>  All the command objects are derived from the DbCommand class.
  =>  The command object is represented by two classes: SqlCommand and OleDbCommand.
  =>  The Command object provides three methods to execute commands on the database:
  =>  The ExecuteNonQuery() method executes the commands and does not return any value.
  =>  The ExecuteScalar() method returns a single value from a database query.
  =>  The ExecuteReader() method returns a result set by using the DataReader object.

One of the major component of ADO.NET is the DataSet object, which always remains disconnected from the database and reduces the load on the database.