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Please read What is dll hell? interview question, before proceeding with this article.
In short, the dll hell problem is solved in .NET by signing the shared assemblies with strong name. Please follow this article, to understand the process of strong naming an assembly.
In dot net all the shared assemblies are usually in the GAC. GAC stands for Global Assembly Cache. The path for GAC is C:\[OperatingSystemDirectory]\assembly. For example on my computer the path is C:\WINDOWS\assembly. The image below shows the shared assemblies in the GAC.
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Only strong named assemblies can be copied into GAC. Strong named assemblies in .NET has 4 pieces in its name as listed below.
1. Simple Textual Name
2. Version Number
3. Culture
4. Public Key Token
All these four pieces put together, is called as the fully qualified name of the assembly. In the GAC image above Accessibility assembly has a version of 2.0.0.0.
Now consider the example below:
1. I have 2 applications, Application - A1 and Application - A2 which relies on the shared assembly Accessibility.dll (Version 2.0.0.0) as shown in the image below.
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2. Now, I have a latest version of Application - A2 available on the internet.
3. I download the latest version of A2 and install it on my machine.
4. This new installation copies a newer version of Accessibility.dll into the GAC with version 3.0.0.0.
5. So, in the GAC we now have 2 versions of Accessibility.dll.
6. Application - A1 continues to use Accessibility.dll (version 2.0.0.0) and Application - A2 uses Accessibility.dll (version 3.0.0.0)
7. So, now the assemblies are able to reside side by side in the GAC. For this reason dot net assemblies are also said to be supporting side by side execution.
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veknat,i ma very thankufull to you,you have picturesqued the dll hell problem..it s superb explnation.once agian thanku
ReplyDeletehi,
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very good simple and to the point Bravo!!
Really good one
ReplyDeletei dont know .net.. but i got it
ReplyDeleteIN DLL HELL PROBLEM WHERE IS THE SHARED ASSEMBLY STORED.I STUDIED THAT SHARED ASSEMBLIES ARE IN GAC.
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hi i m gaurav
ReplyDeleteu can use very simple language to understand the question.
and it benifit for me i learn soo much from your site
Nice article for beginners and for the expertise as well
ReplyDeleteYou should have explained the problem first, then you can provide the solution. I don't find any clear explanation of the problem "DLL Hell". Allyou have provided is a solution of an Unexplained question.
ReplyDeleteHi Venkat,
ReplyDeleteDLL Hell solved in .net framework explanation with pictorial representation is nice which is easily understand by every one..
If latest version of A2 and installed it on my machine.How it will copy the new version of the assembly into the assebly filder witjout running the gacutil.Could u calrifty?
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Thank you again.
I have never seen a better explanation..
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