A similar question was asked here, but was specific to .NET 3.5. Specifically, I'm looking for the following:
Enumerate the subkeys of HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP. Each subkey is a .Net version. It should have Install=1 value if it's present on the machine, an SP value that shows the service pack and an MSI=1 value if it was installed using an MSI. (.Net 2.0 on Vista doesn't have the last one for example, as it is part of the OS)
The registry is the "official" way to detect if a specific version of the Framework is installed, but which registry keys are needed change depending on the Framework version you are looking for.
Framework Version Registry Key ------------------------------------------------------------------------------------------ 1.0 HKLM\Software\Microsoft\.NETFramework\Policy\v1.0\3705 1.1 HKLM\Software\Microsoft\NET Framework Setup\NDP\v1.1.4322\Install 2.0 HKLM\Software\Microsoft\NET Framework Setup\NDP\v2.0.50727\Install 3.0 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.0\Setup\InstallSuccess 3.5 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.5\Install 4.0 Client Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Client\Install 4.0 Full Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Full\Install
The value is also different. For .NET 1.0, the value is a String value; all others use a DWORD.
Determining the service pack level follows a similar pattern:
Framework Version Registry Key
------------------------------------------------------------------------------------------
1.0 HKLM\Software\Microsoft\Active Setup\Installed Components\{78705f0d-e8db-4b2d-8193-982bdda15ecd}\Version
1.0[1] HKLM\Software\Microsoft\Active Setup\Installed Components\{FDC11A6F-17D1-48f9-9EA3-9051954BAA24}\Version
1.1 HKLM\Software\Microsoft\NET Framework Setup\NDP\v1.1.4322\SP
2.0 HKLM\Software\Microsoft\NET Framework Setup\NDP\v2.0.50727\SP
3.0 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.0\SP
3.5 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.5\SP
4.0 Client Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Client\Servicing
4.0 Full Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Full\Servicing
[1] Windows Media Center or Windows XP Tablet Edition
As you can see, determining the SP level for .NET 1.0 changes if you are running on Windows Media Center or Windows XP Tablet Edition. Again, .NET 1.0 uses a string value while all of the others use a DWORD.
For .NET 1.0 the string value at either of these keys has a format of #,#,####,#. The last # is the Service Pack level.
While I didn't explicitly ask for this, if you want to know the exact version number of the Framework you would use these registry keys:
Framework Version Registry Key
------------------------------------------------------------------------------------------
1.0 HKLM\Software\Microsoft\Active Setup\Installed Components\{78705f0d-e8db-4b2d-8193-982bdda15ecd}\Version
1.0[1] HKLM\Software\Microsoft\Active Setup\Installed Components\{FDC11A6F-17D1-48f9-9EA3-9051954BAA24}\Version
1.1 HKLM\Software\Microsoft\NET Framework Setup\NDP\v1.1.4322
2.0[2] HKLM\Software\Microsoft\NET Framework Setup\NDP\v2.0.50727\Version
2.0[3] HKLM\Software\Microsoft\NET Framework Setup\NDP\v2.0.50727\Increment
3.0 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.0\Version
3.5 HKLM\Software\Microsoft\NET Framework Setup\NDP\v3.5\Version
4.0 Client Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Version
4.0 Full Profile HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Version
[1] Windows Media Center or Windows XP Tablet Edition
[2] .NET 2.0 SP1
[3] .NET 2.0 Original Release (RTM)
Again, .NET 1.0 uses a string value while all of the others use a DWORD.
For .NET 1.0 the string value at either of these keys has a format of #,#,####,#. The #,#,#### portion of the string is the Framework version.
For .NET 1.1, we use the name of the registry key itself, which represents the version number.
Finally, if you look at dependencies, .NET 3.0 adds additional functionality to .NET 2.0 so both .NET 2.0 and .NET 3.0 must both evaulate as being installed to correctly say that .NET 3.0 is installed. Likewise, .NET 3.5 adds additional functionality to .NET 2.0 and .NET 3.0, so .NET 2.0, .NET 3.0, and .NET 3. should all evaluate to being installed to correctly say that .NET 3.5 is installed.
.NET 4.0 installs a new version of the CLR (CLR version 4.0) which can run side-by-side with CLR 2.0.
Using the Signum.Utilities library from SignumFramework (wich you can use stand-alone), you can get it nicely and without dealing with the registry by yourself:
AboutTools.FrameworkVersions().ToConsole();
//Writes in my machine:
//v2.0.50727 SP2
//v3.0 SP2
//v3.5 SP1
You can also detect the version and service pack installed, based on Mscorlib.dll file version.
The Framework 4 beta installs to a differing registry key.
using System;
using System.Collections.ObjectModel;
using Microsoft.Win32;
class Program
{
static void Main(string[] args)
{
foreach(Version ver in InstalledDotNetVersions())
Console.WriteLine(ver);
Console.ReadKey();
}
public static Collection<Version> InstalledDotNetVersions()
{
Collection<Version> versions = new Collection<Version>();
RegistryKey NDPKey = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP", true);
if (NDPKey != null)
{
string[] subkeys = NDPKey.GetSubKeyNames();
foreach (string subkey in subkeys)
{
GetDotNetVersion(NDPKey.OpenSubKey(subkey), subkey, versions);
GetDotNetVersion(NDPKey.OpenSubKey(subkey).OpenSubKey("Client"), subkey, versions);
GetDotNetVersion(NDPKey.OpenSubKey(subkey).OpenSubKey("Full"), subkey, versions);
}
}
return versions;
}
private static void GetDotNetVersion(RegistryKey parentKey, string subVersionName, Collection<Version> versions)
{
if (parentKey != null)
{
string installed = Convert.ToString(parentKey.GetValue("Install"));
if (installed == "1")
{
string version = Convert.ToString(parentKey.GetValue("Version"));
if (string.IsNullOrEmpty(version))
{
if (subVersionName.StartsWith("v"))
version = subVersionName.Substring(1);
else
version = subVersionName;
}
Version ver = new Version(version);
if (!versions.Contains(ver))
versions.Add(ver);
}
}
}
}
Small correction for the .NET 4 keys. They are actually here for RTM:
HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\
Not in v4.0.
for 64 bit OS the path would be HKEY_LOCAL_MACHINE\SOFTWARE\wow6432Node\Microsoft\NET Framework Setup\NDP\
There is an official Microsoft answer to this question at the following knowledge base article:
http://support.microsoft.com/kb/318785/en-us
Article ID: 318785 - Last Review: November 7, 2008 - Revision: 20.1 How to determine which versions of the .NET Framework are installed and whether service packs have been applied
Unfortunately, it doesn't appear to work, because the mscorlib.dll version in the 2.0 directory has a 2.0 version, and there is no mscorlib.dll version in either the 3.0 or 3.5 directories even though 3.5 SP1 is installed ... why would the official Microsoft answer be so misinformed?
FWIW... here is another solution that seems to have been widely tested in the real world (but it is in C)