Compiling into a library:

vbc /t:library /out:bin/myLibraryAssembly.dll myCodeBehindFile.vb

You may need to add references to the vb compiler:

vbc /t:library /r:System.dll /r:System.Web.Services.dll /r:System.XML.dll /out:MathService.dll MathService.vb

Compiling into an exe:

vbc /out:mySingleFileAssembly.exe myCodeBehindFile.vb

Note: You may need to set up path variables for your system if using vbc results in a "program not found error". The reason is the system can't find the vbc.exe program. Environment variables can be found in the control panel under "System". Your system path variable should include the paths to your compiler tools:
C:\Program Files\Microsoft.NET\FrameworkSDK\Bin\;
C:\Program Files\Microsoft Visual Studio .NET\Common7\IDE\;
C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\;
If you don't have access to the system variables, you may be able to put the path variable in your user path variable.