.net – ASMX Web Service slow first request

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.

Make sure your problem isn't just JIT or load time. On the first call the webservice has to compile and load assemblies which can be expensive. If the problem persists in later calls then check your proxy settings.

We had the same problem. Our delay was much more significant then yours (2 minutes per call total). We were invoking a web service from inside a windows service that was running as a domain user. That user account apparently has it's proxy settings turned on. So for each HttpRequest to the local web service the backing ServicePoint tried to fetch the wpad.dat file from a non-existant proxy server. That call took 20 seconds to time out. Worse there is a global lock around the code that fetches the proxy in the .net libraries. So calls stack up waiting for web timeout. The service making the calls is our queue process which handles all of our async behavior. So the entire system backed up.

If you want to see the code look at System.Net.AutoWebProxyScriptEngine.GetProxies in Reflector.

Since I don't have rights to the user account in question I fixed our problem today by adding to the app.config file.

If your method is intended to be invoked with ajax then you have to get the browser settings correct. Try disabling Automatically Detect Settings in the Connections\Lan Settings. I looked around the web a bit after I found the problem and apparently IE7 is reported to have latency problems when this setting is on. If you do have a proxy server then manually enter the server address in the same dialog.