VCL is a set of visual components for building Windows applications in the Delphi language. VCL for .NET is the same library of components updated for use in the .NET Framework. VCL for .NET and the .NET Framework coexist within RAD Studio. Both VCL for .NET and .NET provide components and functionality that allow you to build .NET applications:

• VCL for .NET provides the means to create VCL Forms applications, which are Delphi forms that are .NET-enabled, and use VCL for .NET components.
• VCL for .NET provides VCL non-visual components which have been .NET-enabled to access databases. You can also access databases through the ADO.NET and BDP.NET providers.
• .NET provides the means to build .NET Web Forms and Console applications, using .NET components, with Delphi code-behind.

You can build VCL Forms applications using VCL for .NET components. You can also build ASP.NET Web Forms applications using either VCL for .NET components or .NET components.

The .NET Framework provides a library of components, classes, and low-level functionality that manages much of the common functionality, from the display of buttons to remoting functionality, without regard to the underlying implementation language. VCL for .NET and the .NET Framework are functionally equivalent. Like the .NET Framework, VCL for .NET provides libraries of components, controls, classes, and low-level functionality that help you build Web Forms and console applications that run on the current Windows .NET Framework platform.  

VCL for .NET is not a replacement for the .NET Framework. 

You will still need the .NET runtime to use VCL for .NET, but you can build complete applications using VCL for .NET components that will run on .NET platform.  

You can build RAD Studio applications without using VCL for .NET, by creating Web Forms and Console applications using RAD Studio code.  

You can use RAD Studio to create powerful .NET applications using .NET components, or VCL for .NET components that have been migrated from the Delphi VCL. If you have existing Delphi VCL applications that you want to run on Windows XP, you can easily port those applications by using RAD Studio.

VCL for .NET consists of a set of visual and non-visual components. VCL for .NET builds on the concept of constructing applications visually, eliminating much manual coding.

RAD Studio provides a set of visual components, or controls, that you can use to build your applications. In addition to the common controls, such as buttons, text boxes, radio buttons, and check boxes, you can also find grid controls, scroll bars, spinners, calendar objects, a full-featured menu designer, and more. These controls are represented differently in RAD Studio than they are in frameworks, such as the .NET Framework.  

In an IDE for other languages, such as C# or Java, you will see code-centric representations of forms and other visual components. These representations include physical definitions, such as size, height, and other properties, as well as constructors and destructors for the components. In the Code Editor of RAD Studio you will not see a code representation of your VCL for .NET components. 

RAD Studio is a resource-centric system, which means that the primary code-behind representations are of event handlers that you fill in with your program logic. Visual components are declared and defined in text files with the extensions .dfm (Delphi Forms) or .nfm (RAD Studio forms). The nfm files are created by RAD Studio as you design your VCL Forms on the Forms Designer, and are listed in the resource list in the Project Manager for the given project.

You can use non-visual components to implement functionality that is not necessarily exposed visually. For example, you can access data by using non-visual components like the BDP.NET components, which provide database connectivity and DataSet access. Even though these components do not have visual runtime behavior, they are represented by components in the Tool Palette at designtime. VCL for .NET provides a variety of non-visual components for data access, server functions, and more.

VCL for .NET classes are found under the Borland.Vcl namespace. Database-related classes are in the Borland.Vcl.DB namespace. Runtime library classes are in the Borland.Vcl.Rtl namespace. 

Unit files have been bundled in corresponding Borland.Vcl namespaces. In some cases, units have been moved. However, namespaces are identified in a way that will assist you in finding the functionality you want.  

Source files for all of the RAD Studio objects are available in the c:\Program Files\CodeGear\RAD Studio\5.0\Source subdirectory.

If you have existing applications written with an earlier version of Delphi, you might want to port them to .NET. In most cases, this will be easier than rewriting the applications. Because RAD Studio takes advantage of significant structural elements in the .NET Framework, you will need to perform some manual porting tasks to make your applications run. For example, the .NET Framework does not support pointers in safe code. So, any instance of a pChar or pointer variable will need to be changed to a .NET type. Many Delphi objects have been updated to accommodate these type restrictions, but your code may include references to pointers or unsupported types. For more information, refer to the Language Guide in this Help system.

RAD Studio provides the .NET Import Wizard to help you import .NET controls into VCL for .NET units and packages. For example, you can wrap all .NET components, like those from the System.Windows.Forms assembly, in ActiveX wrappers that can be deployed on VCL for .NET applications. Once you have imported the .NET components of your choice, you can add a completed package file containing the units for each component to the Tool Palette. You can also view and modify the individual unit files, which can be useful reference material when you are writing your own custom components.

Language Guide 

Porting VCL Applications 

Data Providers for .NET 

Importing .NET Controls to VCL for .NET 

Deploying Applications 

Building a VCL for .NET Form Application