In this blog, I’m explaining the dll hell problem in .net
refers to the set of problems caused when multiple applications attempt to
share a common component like a dynamic-link library (DLL) or a Component
Object Model (COM) class. In the most typical case, one application will
install a new version of the shared component that is not backward compatible
with the version already on the machine. Although the application that has just
been installed works fine, existing applications that depended on a previous
version of the shared component might no longer work. In some cases, the cause
of the problem is even more subtle.
Consider the scenario where a user downloads a
Microsoft ActiveX® control as a side effect of visiting some Web site. When the
control is downloaded it will replace any existing versions of the control that
were present on the machine. If an application that has been installed on the
machine happens to use this control, it too might potentially stop working.
Solution of Dll-Hell Problem
This problem of dynamic link library (.dll) is resolved through
Versioning is the technique
to provide version to the .dll to prevent them from replacement. Each assembly
has a version name called compatibility version, also each reference to an
assembly (from another assembly) includes both the name and version of the
referenced assembly. The version number has four numeric parts (e.g. 220.127.116.11).
Assemblies with either of the first two parts different are normally viewed as
incompatible. If the first two parts are same but the third is different, the
assemblies are deemed as may be incompatible. If only the fourth part is
different, the assemblies are deemed as compatible.
DLL name template: Dll_name_xx.dll where xx is the number of the DLL version. Sometimes it is required to make big
changes in the DLL, which break its backwards compatibility. In this case, the
new name should be assigned to the DLL. While an installation to an OS, a new
DLL, the old one will not be removed and clients compiled with it will still
use it. At the same time, clients compiled with the new DLL will use the new