If you build a custom client user interface or some piece of middleware using .NET that communicates programmatically to an Infinity instance, one question that arises is "Which .NET version should I use?" The answer depends on whether you access the AppFxWebService.asmx web service directly through a web service reference or through one of the various middleware .NET assembly "wrappers" that call the AppFxWebService.asmx on your behalf.
The short answer is the AppFxWebService.asmx or BizOp ASMX SOAP web service endpoints rely on .NETversion 2.0. However, the Blackbaud.AppFx.WebApi.dll or one of the Blackbaud.AppFx.*.WebAPIClient.dll assemblies within the Blackbaud Infinity SDK have a dependency on .NET version 4.0.
If you only rely on the Blackbaud AppFx Web Service (AppFxWebService.asmx), you will not have any dependencies to the Infinity SDK. Therefore, you can use just about any version of the .NET Framework from 2.0 to 4.0. You also can use either Visual Studio 2008 or 2010 to build the client application. However, if you set references to any of Infinity SDK assemblies that have a dependency on the .NET Framework 4.0, you need to utilize .NET Framework 4.0 and Visual Studio 2010.