Is there a command line command for verifying what version of .NET is installed

Question

Since you said you want to know if its actually installed, I think the best way (short of running version specific code), is to check the reassuringly named "Install" registry key. 0x1 means yes:

C:\>reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5"| findstr Install

   Install     REG_DWORD       0x1
   InstallPath REG_SZ  c:\WINNT\Microsoft.NET\Framework\v3.5\

This also happens to be the "Microsoft Recommended" official method.

WMI is another possibility, but seems impractical (Slow? Takes 2 min on my C2D, SSD). Maybe it works better on your server:

C:\>wmic product where "Name like 'Microsoft .Net%'" get Name, Version

Name                                                Version
Microsoft .NET Compact Framework 1.0 SP3 Developer  1.0.4292
Microsoft .NET Framework 3.0 Service Pack 2         3.2.30729
Microsoft .NET Framework 3.5 SP1                    3.5.30729
Microsoft .NET Compact Framework 2.0                2.0.5238
Microsoft .NET Framework 4 Client Profile           4.0.30319
Microsoft .NET Framework 4 Multi-Targeting Pack     4.0.30319
Microsoft .NET Framework 2.0 Service Pack 2         2.2.30729
Microsoft .NET Framework 1.1                        1.1.4322
Microsoft .NET Framework 4 Extended                 4.0.30319

C:\>wmic product where "name like 'Microsoft .N%' and version='3.5.30729'" get name

Name  
Microsoft .NET Framework 3.5 SP1

Other than these I think the only way to be 100% sure is to actually run a simple console app compiled targeting your framework version. Personally, I consider this unnecessary and trust the registry method just fine.

Finally, you could set up an intranet test site which is reachable from your server and sniffs the User Agent to determine .NET versions. But that's not a batch file solution of course. Also see doc here.

You mean a DOS command such as below will do the job displaying installed .NET frameworks:

wmic /namespace:\\root\cimv2 path win32_product where "name like '%%.NET%%'" get version

The following may then be displayed:

Version
4.0.30319

WMIC is quite useful once you master using it, much easier than coding WMI in scripts depending on what you want to achieve.

Unfortunately the best way would be to check for that directory. I am not sure what you mean but "actually installed" as .NET 3.5 uses the same CLR as .NET 3.0 and .NET 2.0 so all new functionality is wrapped up in new assemblies that live in that directory. Basically, if the directory is there then 3.5 is installed.

Only thing I would add is to find the dir this way for maximum flexibility:

%windir%\Microsoft.NET\Framework\v3.5

You can write yourself a little console app and use System.Environment.Version to find out the version. Scott Hanselman gives a blog post about it.

Or look in the registry for the installed versions. HKLM\Software\Microsoft\NETFramework Setup\NDP

If you're going to run a little console app, you may as well install clrver.exe from the .NET SDK. I don't think you can get cleaner than that. This isn't my answer (but I happen to agree), I found it here.