The registry is the official way to detect if a specific version of the Framework is installed.
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
Generally you are looking for:
"Install"=dword:00000001
except for .NET 1.0, where the value is a string (REG_SZ
) rather than a number (REG_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.
Additional Notes
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.
Update for .NET 4.5
There won't be a v4.5
key in the registry if .NET 4.5 is installed. Instead you have to check if the HKLM\Software\Microsoft\NET Framework Setup\NDP\v4\Full
key contains a value called Release
. If this value is present, .NET 4.5 is installed, otherwise it is not. More details can be found here and here.
C# language version history:
These are the versions of C# known about at the time of this writing:
- C# 1.0 released with .NET 1.0 and VS2002 (January 2002)
- C# 1.2 (bizarrely enough); released with .NET 1.1 and VS2003 (April 2003). First version to call
Dispose
on IEnumerator
s which implemented IDisposable
. A few other small features.
- C# 2.0 released with .NET 2.0 and VS2005 (November 2005). Major new features: generics, anonymous methods, nullable types, and iterator blocks
- C# 3.0 released with .NET 3.5 and VS2008 (November 2007). Major new features: lambda expressions, extension methods, expression trees, anonymous types, implicit typing (
var
), and query expressions
- C# 4.0 released with .NET 4 and VS2010 (April 2010). Major new features: late binding (
dynamic
), delegate and interface generic variance, more COM support, named arguments, tuple data type and optional parameters
- C# 5.0 released with .NET 4.5 and VS2012 (August 2012). Major features: async programming, and caller info attributes. Breaking change: loop variable closure.
- C# 6.0 released with .NET 4.6 and VS2015 (July 2015). Implemented by Roslyn. Features: initializers for automatically implemented properties, using directives to import static members, exception filters, element initializers,
await
in catch
and finally
, extension Add
methods in collection initializers.
- C# 7.0 released with .NET 4.7 and VS2017 (March 2017). Major new features: tuples, ref locals and ref return, pattern matching (including pattern-based switch statements), inline
out
parameter declarations, local functions, binary literals, digit separators, and arbitrary async returns.
- C# 7.1 released with VS2017 v15.3 (August 2017). New features: async main, tuple member name inference, default expression, and pattern matching with generics.
- C# 7.2 released with VS2017 v15.5 (November 2017). New features: private protected access modifier, Span<T>, aka interior pointer, aka stackonly struct, and everything else.
- C# 7.3 released with VS2017 v15.7 (May 2018). New features: enum, delegate and
unmanaged
generic type constraints. ref
reassignment. Unsafe improvements: stackalloc
initialization, unpinned indexed fixed
buffers, custom fixed
statements. Improved overloading resolution. Expression variables in initializers and queries. ==
and !=
defined for tuples. Auto-properties' backing fields can now be targeted by attributes.
- C# 8.0 released with .NET Core 3.0 and VS2019 v16.3 (September 2019). Major new features: nullable reference-types, asynchronous streams, indices and ranges, readonly members, using declarations, default interface methods, static local functions, and enhancement of interpolated verbatim strings.
- C# 9.0 released with .NET 5.0 and VS2019 v16.8 (November 2020). Major new features: init-only properties, records, with-expressions, data classes, positional records, top-level programs, improved pattern matching (simple type patterns, relational patterns, logical patterns), improved target typing (target-type
new
expressions, target typed ??
and ?
), and covariant returns. Minor features: relax ordering of ref
and partial
modifiers, parameter null checking, lambda discard parameters, native int
s, attributes on local functions, function pointers, static lambdas, extension GetEnumerator
, module initializers, and extending partial.
In response to the OP's question:
What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?
There is no such thing as C# 3.5 - the cause of confusion here is that the C# 3.0 is present in .NET 3.5. The language and framework are versioned independently, however - as is the CLR, which is at version 2.0 for .NET 2.0 through 3.5, .NET 4 introducing CLR 4.0, service packs notwithstanding. The CLR in .NET 4.5 has various improvements, but the versioning is unclear: in some places it may be referred to as CLR 4.5 (this MSDN page used to refer to it that way, for example), but the Environment.Version
property still reports 4.0.xxx.
As of May 3, 2017, the C# Language Team created a history of C# versions and features on their GitHub repository: Features Added in C# Language Versions. There is also a page that tracks upcoming and recently implemented language features.
Best Answer
Yes, and no.
Most versions of ASP.NET and the CLR correspond, but there are some versions of ASP.NET that comes without a new version of the CLR:
Edit:
ASP.NET versions and .NET framework versions are the same. The usage of the ASP.NET versions does however differ a bit depending on what you do.
When you create a web application in Visual Studio, you can specify the target framework. This determines what libraries you can use, so ASP.NET 2.0 and ASP.NET 3.5 have different capabilities. In that sense all the above versions exist.
When you install the application on a web server, all applications in the same application pool have to run the same version of the framework, but it's actually the version of the CLR that is relevant. An ASP.NET 2.0 application can run in the same application pool as an ASP.NET 3.5 application. When you select ASP.NET/framework version in IIS it's actually only the CLR versions that you choose from, so in that sense the ASP.NET version 3.0 and 3.5 does not exist.