I am using IIS 7.0 + Windows Server 2008 x64. I have installed .NET Framework 3.5 on my machine, but from the IIS 7.0 application pool .NET framework settings, I could only set version to v1.0 or v2.0. Why can't I set to version v3.5 — which is the latest version of .NET framework I installed on my machine?
R – .NET Framework version issue
iisnetversion
Related Solutions
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
onIEnumerator
s which implementedIDisposable
. 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
incatch
andfinally
, extensionAdd
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 indexedfixed
buffers, customfixed
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 ofref
andpartial
modifiers, parameter null checking, lambda discard parameters, nativeint
s, attributes on local functions, function pointers, static lambdas, extensionGetEnumerator
, 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.
float
and double
are floating binary point types. In other words, they represent a number like this:
10001.10010110011
The binary number and the location of the binary point are both encoded within the value.
decimal
is a floating decimal point type. In other words, they represent a number like this:
12345.65789
Again, the number and the location of the decimal point are both encoded within the value – that's what makes decimal
still a floating point type instead of a fixed point type.
The important thing to note is that humans are used to representing non-integers in a decimal form, and expect exact results in decimal representations; not all decimal numbers are exactly representable in binary floating point – 0.1, for example – so if you use a binary floating point value you'll actually get an approximation to 0.1. You'll still get approximations when using a floating decimal point as well – the result of dividing 1 by 3 can't be exactly represented, for example.
As for what to use when:
For values which are "naturally exact decimals" it's good to use
decimal
. This is usually suitable for any concepts invented by humans: financial values are the most obvious example, but there are others too. Consider the score given to divers or ice skaters, for example.For values which are more artefacts of nature which can't really be measured exactly anyway,
float
/double
are more appropriate. For example, scientific data would usually be represented in this form. Here, the original values won't be "decimally accurate" to start with, so it's not important for the expected results to maintain the "decimal accuracy". Floating binary point types are much faster to work with than decimals.
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Best Answer
To answer the comment that George2 has left to each of the other answers in one place:
Yes. The Common Language Runtime is what needs to be 2.0 (and cannot, currently, be higher, since that's the latest at this time).
Yes. You can think of the .NET Framework as the SDK if that makes it easier. It's not quite accurate, but....
Yes. You will be deploying your Framework 3.5 functionality on the CLR 2.0. Confusing, but that's Microsoft for you. They do (some) great work, but seem to delight in confusing users with arbitrary versioning.