Determine .NET Framework version for dll

Question

I have an old dll that was compiled against the .NET framework and deployed. I am not sure which version of the .NET framework it was compiled against. I am wondering how I can determine which version of the .NET framework this dll was compiled against? I cannot trust the source code because I believe it has been upgraded to Visual Studio 2008 and changed to .NET framework version 3.5.

Monopolize

Possible duplicate of How to find out which version of the .NET Framework an executable needs to run? – Odilia

Answer 1

Load it into Reflector and see what it references?

for example:

Jansen

My idea too, but knowing reflector, it will probably complain, and give it a nice non-descript error icon. – Polyptych

@Polyptych Shouldn't be a problem, even if it's .NET 1.1. Just change your default assembly list. – Jansen

Your answer is very helpful, but I advise not to rely on it blindly -- yesterday I spent too much time on my own project which was targeted for .Net 4.0, reported by Reflector to use .Net 4.0.3, and required to use .Net 4.5 by Windows :-) I don't know any method to verify this on project other than with sources -- see here: #13215003 – Strickland

You can also use the free, open-source alternative ILSpy as noted by Kat Lim Ruiz. – Huysmans

This answer worked for me: https://mcmap.net/q/135953/-determine-net-framework-version-for-dll. – Reinaldo

Answer 2

In PowerShell you can use the following to get the target runtime:

$path = "C:\Some.dll"
[Reflection.Assembly]::ReflectionOnlyLoadFrom($path).ImageRuntimeVersion

I adapted this to PowerShell from Ben Griswold's answer.

If you want to know the target framework version specified in Visual Studio, use:

$path = "C:\Some.dll"
[Reflection.Assembly]::ReflectionOnlyLoadFrom($path).CustomAttributes |
Where-Object {$_.AttributeType.Name -eq "TargetFrameworkAttribute" } | 
Select-Object -ExpandProperty ConstructorArguments | 
Select-Object -ExpandProperty value

You should get something like

.NETFramework,Version=v4.5.2

Vimen

This answer is the most helpful. All Windows OSes after 2003 support Powershell. A shell giving immediate feedback, not requiring any additional application support as many of the other answers suggest. Great for a "one off" check of a dll. you're the man @swoogan. – Management

I did this for a DLL I built with a TargetFrameworkVersion of v3.5, and it returned v2.0.50727. What am I missing? – Luxuriance

@Luxuriance there have only really been 4 runtime versions: 1.0, 1.1, 2.0 and 4.0. .NET 3.0 and 3.5 compile to CLR version 2.0. msdn.microsoft.com/en-us/library/bb822049(v=vs.110).aspx – Vimen

Neat, and scriptable by design too. – Boor

This script only provides RuntimeVersion, question is about TargetFrameworkversion. Effectively for all assemblies compiled against 2.0,3.0,3.5 this script shows the Runtime version as 2.0.0.0 – Loxodromics

@KiranVedula as I specified, I adapted this from another answer. However, you make a good point. I updated the answer to add the TargetFrameworkVersion. – Vimen

For me the ReflectionOnlyLoadFrom returns the ImageRuntimeVersion but zero CustomAttributes. Using LoadFrom instead of ReflectionOnlyLoadFrom gives the expected result. Any reason? PSVersion 5.1.16299.251 CLRVersion 4.0.30319.42000 – Campbell

Looks like my assembly does not have "TargetFrameworkAttribute". It does have ImageRuntimeVersion. But I want the target framework version for which a binary was built for. What could be wrong? – Backache

I also got nothing from ReflectionOnlyLoadFrom and "LoadFrom" fixed it. I'm guessing it's because the DLLs are dotnet standard, and maybe that doesn't support reflection? – Highboy

This doesn't run so well using PowerShell 7. But it does work fine using the older Windows PowerShell. – Reproachless

Absolutely nothing is displayed in my powershell – Brachio

Answer 3

dotPeek is a great (free) tool to show this information.

If you are having a few issues getting hold of Reflector then this is a good alternative.

Brighten

FYI, I switched from DotPeek to JustDecompile because of one issue: if you select "specific version = false," DotPeek showed an empty version, and JustDecompile shows the correct version. Made it worth switching for me. – Gunpowder

Great - did exactly what I've wanted without install a trial for Reflector. – Personate

Answer 4

You can use ILDASM...

ildasm.exe C:\foo.dll /metadata[=MDHEADER] /text /noil

and check for the 'Metadata section' in the output. It would be something like this:

Metadata section: 0x424a5342, version: 1.1, extra: 0, version len: 12, version: v4.0.30319

The 'version' tag will tell you the .NET Framework version. In the above example it is 4.0.30319

Sapindaceous

What am I looking for here? Does this mean .NET 4.0? // Metadata section: 0x424a5342, version: 1.1, extra: 0, version len: 12, versio n: v4.0.30319 – Zwick

Yes, for .NET 2 I get the following: // Metadata section: 0x424a5342, version: 1.1, extra: 0, version len: 12, version: v2.0.50727 – Vue

But that’s the CLR version, not .NET Framework version. – Hensel

Answer 5

You have a few options: To get it programmatically, from managed code, use Assembly.ImageRuntimeVersion:

Dim a As Assembly = Reflection.Assembly.ReflectionOnlyLoadFrom("C:\path\assembly.dll")
Dim s As String = a.ImageRuntimeVersion

From the command line, starting in v2.0, ildasm.exe will show it if you double-click on "MANIFEST" and look for "Metadata version". Determining an Image’s CLR Version

Rooftop

How get ImageRuntimeVersion for CurrentAppDomain ? – Virgil

Answer 6

Use ILSpy http://ilspy.net/

open source, free, definitely an option since now reflector is paid.

Keare

Answer 7

Just simply

var tar = (TargetFrameworkAttribute)Assembly
          .LoadFrom("yoursAssembly.dll")
          .GetCustomAttributes(typeof(TargetFrameworkAttribute)).First();

Scarface

I don't know why this has been downvoted, but I can run the snippet (a reference to System.Runtime.Versioning is needed) and successfully get the output (this is from LINQPad): TypeId typeof (TargetFrameworkAttribute) FrameworkName .NETFramework,Version=v4.0 FrameworkDisplayName .NET Framework 4 – Shawnee

This code doesn't retrieve the full version of the framework. "4.0" is good to know, but "v4.0.30319" would be more useful if you were, say, trying to get to RegAsm.exe. The more complete version information can be found in: string tar = Assembly.LoadFrom(@"myAssembly.dll").ImageRuntimeVersion; – Inadmissible

This seems like the right approach, is there any circumstances where an assembly might not have this attribute applied? I've tested it with a .NET Core assembly and it correctly reports netcore and the version number. – Pincince

This does not work for me. The GetCustomAttributes does not have a TargetFrameworkAttribute. But ImageRuntimeVersion works fine though, it retrieves the right CLR the binary was built for. I need the target framework version for which it was built. – Backache

It is far more complicated than that. This answer only works for .NET Framework 4.x and compiled by Microsoft C# compilers. It does not apply to the actual question. – Hensel

@LexLi you need to understand that this question is 12yrs old and .net 4 was the latest one running at that time. The answer is relative to the time of question was raised. – Scarface

Answer 8

Yet another option via Visual Studio, add a reference to the DLL to any project, then right-clicking on the new reference and click Properties, you can see what you are looking for in Runtime version:

Emelia

I think this question is not asking about when a DLL is referenced in Visual Studio, but any ol' .NET DLL you find lying around on your PC. – Gunpowder

This answer indicates that you can add a reference to any ol' .NET DLL you find lying around on your PC, and one of the properties of the item under the References corresponding to that DLL is the "Runtime Version". – Malocclusion

That’s the CLR version, not the .NET Framework version being asked. – Hensel

Answer 9

The simplest way: just open the .dll in any text editor. Look at one of the last lines:

For .Net 8.0 the string is slightly updated .NETCoreApp,Version=v8.0

Horme

The best option among all – Writ

However, this doesn't work for dlls built before .Net 3.0 – Writ

@Writ There's no such thing as ".NET 3.0" - I assume you meant to say .NET Core 3.x instead? (as not to get confused by 2006's .NET Framework 3.0 which confusingly actually ran on the .NET Framework 2.0 CLR) – Stipend

I used this approach for my answer below. I only handled .NETFramework and .NETCoreApp but it is working for what I need. https://mcmap.net/q/135953/-determine-net-framework-version-for-dll – Mcmillan

Answer 10

Decompile it with ILDASM, and look at the version of mscorlib that is being referenced (should be pretty much right at the top).

Polyptych

Answer 11

If you have dotPeek from JetBrains, you can see it in Assembly Explorer.

Inerrant

Answer 12

I quickly wrote this C# console app to do this:

https://github.com/stuartjsmith/binarydetailer

Simply pass a directory as a parameter and it will do its best to tell you the net framework for each dll and exe in there

Suburbia

Gives good detailed info; it's a command-line app; you have to pass it the directory name on the command-line. – Dashing

Answer 13

"Detect It Easy" also known as DiE is a program for determining types of files. Works with .dll files or other (.exe) files. Absolute free for commercial and non-commercial use.

Stuart

Answer 14

Using the "read the text contents of the dll" approach:

private static readonly Regex CompiledNetCoreRegex = new Regex(@".NETCoreApp,Version=v[0-9\.]+", RegexOptions.Compiled);
private static readonly Regex CompiledNetFrameworkRegex = new Regex(@".NETFramework,Version=v[0-9\.]+", RegexOptions.Compiled);

// You can define other methods, fields, classes and namespaces here
public string GetTargetFramework(FileInfo dll)
{
    string contents = File.ReadAllText(dll.FullName);
 
    Match match = CompiledNetCoreRegex.Match(contents);
    if (match.Success)
    {
        return match.Value;
    }

    match = CompiledNetFrameworkRegex.Match(contents);
    if (match.Success)
    {
        return match.Value;
    }

    return "unable to compute target framework";
}

Mcmillan

I had to create a tool that finds out witch applications were built targeting an out of support .Net (core) framework. This method does what it should do. Looping through a whole directory, it gave me a list of all used .Net frameworks. Helped a lot :) – Youngran

Answer 15

Expanding on the answers here, this can blow up if there is a dependent assembly. If you're lucky and you know where the dependent is (or even luckier, it's in the GAC) then this may help ...

using System.Reflection;
using System.Runtime.Versioning;
// ...
{
    AppDomain.CurrentDomain.ReflectionOnlyAssemblyResolve += new ResolveEventHandler(CurrentDomain_ReflectionOnlyAssemblyResolve);
    var asm = System.Reflection.Assembly.LoadFrom(@"C:\Codez\My.dll");
    var targetFrameAttribute = asm.GetCustomAttributes(true).OfType<TargetFrameworkAttribute>().FirstOrDefault();
    targetFrameAttribute.Dump();
}

Assembly CurrentDomain_ReflectionOnlyAssemblyResolve(object sender, ResolveEventArgs args)
{
    var name = args.Name;

    if (name.StartsWith("Depends"))
        return System.Reflection.Assembly.ReflectionOnlyLoadFrom(@"C:\Codez\Depends.dll");

    return System.Reflection.Assembly.ReflectionOnlyLoad(args.Name);
}

Reference: https://weblog.west-wind.com/posts/2006/Dec/22/Reflection-on-Problem-Assemblies

Nurture

Answer 16

If you're on Linux and have mono, I think you can use ikdasm instead of ildasm.exe.

I don't really understand this, so I don't know if it's accurate. But I made a simple test compiling a dll library, changing only <TargetFramework>. Then I ran this on the output (bin) dir:

ikdasm -assemblyref lib.dll

The result is different for each target framework.

net8.0

AssemblyRef Table
1: Version=8.0.0.0
        Name=System.Runtime
        Flags=0x00000000
        Public Key:
0x00000000: B0 3F 5F 7F 11 D5 0A 3A

netstandard2.1

AssemblyRef Table
1: Version=2.1.0.0
        Name=netstandard
        Flags=0x00000000
        Public Key:
0x00000000: CC 7B 13 FF CD 2D DD 51

net4.8

AssemblyRef Table
1: Version=4.0.0.0
        Name=mscorlib
        Flags=0x00000000
        Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89

This one seems to show only major version, so:

ikdasm -customattr lib.dll | grep System.Runtime.Versioning.TargetFrameworkAttribute

5: Assembly: 1 instance void class [mscorlib]System.Runtime.Versioning.TargetFrameworkAttribute::'.ctor'(System.String) [".NETFramework,Version=v4.8", {FrameworkDisplayName = ""}]

Izak