what is dll in c#.net

Stands for "Dynamic Link Library." A DLL (.dll) file contains a library of functions and other information that can be accessed by a Windows program. When a program is launched, links to the necessary .dll files are created. If a static link is created, the .dll files will be in use as long as the program is active. If a dynamic link is created, the .dll files will only be used when needed. Dynamic links help programs use resources, such as memory and hard drive space, more efficiently.

DLL files can also be used by more than one program. In fact, they can even be used by multiple programs at the same time. Some DLLs come with the Windows operating system while others are added when new programs are installed. You typically don't want to open a .dll file directly, since the program that uses it will automatically load it if needed. Though DLL filenames usally end in ".dll," they can also end in .exe, .drv, and .fon, just to make things more confusing.

File extension: .DLL

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A .dll file contains compiled code you can use in your application to perform specific program functions and may be required by another application or module (such as .exe or .dll) to load it through an entry point. It is a library that contains code and data that can be used by more than one program at the same time. It helps promote modularization of code, code reuse, efficient memory usage, and reduced disk space. So the operating system and the programs load faster, run faster, and take less disk space on the computer.

What is .Net dll ?

When you implement a .Net DLL (Assembly) in .NET Languages such as C# or VB.NET you produce a Managed Assembly. Managed Assembly is the component standard specified by the .NET. Hence, .Net assemblies are understandable only to Microsoft.NET and can be used only in .NET managed applications. A manage assembly contains managed code and it is executing by the .NET Runtime. When you create a DLL with C++ you produce a win32/Com DLL. If you use this dll in a .NET Language, the Visual Studio create automatically an INTEROP file for you, so you can call the "unmanaged" dll from manage code .

For using a .Net DLL (Assembly), the simplest option is to copy the dll to the bin folder. Normal DLL files are need to be register with the "regsvr32" tool.