Web Application Project Assembly references stored

asp.netassembliesweb.config

Where are assembly refernces stored for a web application?

In a Web Site, I see assembly tags written to the assembly node in the web.config when you add a reference. I am just curious as to how the Web Application Project makes the connection to get the correct local dll?

I manually add the reference and the application builds, but the dll is not imported into the BIN folder, and the assembly nodes are not created in the web config as they are in a Web Site. I do a solution search for the text 'assembly="SomeAssembly…" and no results are found.

I am just curious as I am trying to centralize updating assembly references as a 3rd party control vendor puts out hotfixes on a regular basis and we end up having to run around and update all the individual page refernces to the assembly. I was able to do this effectively in the Web Site project, but I am fairly new to Web Application Projects. Any advice or links would be appreciated. I guess I'm looking for tips on assembly & control reference management for ASP.NET Web Application Projects.

Best Answer

Like most Visual Studio projects, references are kept in the project.

There are two kinds of reference:

Project References are references to another project in the same solution. They look like this:

<ProjectReference Include="..\VBClassLibrary1\VBClassLibrary1.vbproj">
  <Project>{045D7D9F-8E44-4C4B-95F8-620E86593C5B}</Project>
  <Name>VBClassLibrary1</Name>
</ProjectReference>

File references are references to an arbitrary file on disk:

<Reference Include="System.Core">
  <RequiredTargetFramework>3.5</RequiredTargetFramework>
</Reference>

If you expand the References folder and click on a reference, then look in the Properties window, you'll see that both kinds of reference have a "Copy Local" property. For project references it defaults to true, for file references to false (though maybe that's only if the file is in the GAC). Changing the default adds:

  <Private>False</Private>

Website:

The Web Site project is compiled on the fly. You end up with a lot more DLL files, which can be a pain. It also gives problems when you have pages or controls in one directory that need to reference pages and controls in another directory since the other directory may not be compiled into the code yet. Another problem can be in publishing.

If Visual Studio isn't told to re-use the same names constantly, it will come up with new names for the DLL files generated by pages all the time. That can lead to having several close copies of DLL files containing the same class name, which will generate plenty of errors. The Web Site project was introduced with Visual Studio 2005, but it has turned out not to be popular.

Web Application:

The Web Application Project was created as an add-in and now exists as part of SP 1 for Visual Studio 2005. The main differences are the Web Application Project was designed to work similarly to the Web projects that shipped with Visual Studio 2003. It will compile the application into a single DLL file at build time. To update the project, it must be recompiled and the DLL file published for changes to occur.

Another nice feature of the Web Application project is it's much easier to exclude files from the project view. In the Web Site project, each file that you exclude is renamed with an excluded keyword in the filename. In the Web Application Project, the project just keeps track of which files to include/exclude from the project view without renaming them, making things much tidier.

Reference

The article ASP.NET 2.0 - Web Site vs Web Application project also gives reasons on why to use one and not the other. Here is an excerpt of it:

You need to migrate large Visual Studio .NET 2003 applications to VS 2005? use the Web Application project.

You want to open and edit any directory as a Web project without creating a project file? use Web Site project.

You need to add pre-build and post-build steps during compilation? use Web Application project.

You need to build a Web application using multiple Web projects? use the Web Application project.

You want to generate one assembly for each page? use the Web Site project.

You prefer dynamic compilation and working on pages without building entire site on each page view? use Web Site project.

You prefer single-page code model to code-behind model? use Web Site project.

Web Application Projects versus Web Site Projects (MSDN) explains the differences between the web site and web application projects. Also, it discusses the configuration to be made in Visual Studio.

C# – load a .NET assembly at runtime and instantiate a type knowing only the name

Yes. You need to use Assembly.LoadFrom to load the assembly into memory, then you can use Activator.CreateInstance to create an instance of your preferred type. You'll need to look the type up first using reflection. Here is a simple example:

Assembly assembly = Assembly.LoadFrom("MyNice.dll");

Type type = assembly.GetType("MyType");

object instanceOfMyType = Activator.CreateInstance(type);

Update

When you have the assembly file name and the type name, you can use Activator.CreateInstance(assemblyName, typeName) to ask the .NET type resolution to resolve that into a type. You could wrap that with a try/catch so that if it fails, you can perform a search of directories where you may specifically store additional assemblies that otherwise might not be searched. This would use the preceding method at that point.

Best Answer

Related Solutions

.net – ASP.NET Web Site or ASP.NET Web Application

Website:

Web Application:

C# – load a .NET assembly at runtime and instantiate a type knowing only the name

Update

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