Determine framework (CLR) version of assembly

From the command line (or by any means really), how can I determine which CLR version a .NET assembly requires?

I need to determine if an assembly requires 2.0 or 4.0 CLR version.

Solution 1:

ildasm.exe will show it if you double-click on "MANIFEST" and look for "Metadata version". By default, it's the version that the image was compiled against.

Solution 2:

One clarification...

The problem with all the mentioned methods is that they will return version 4.0 if assembly was compiled against .NET framework 4.0, 4.5 or 4.5.1.

The way to figure out this version programmatically at runtime is using the System.Runtime.Versioning.TargetFrameworkAttribute for the given assembly, for example

using System;
using System.Linq;
using System.Reflection;
using System.Runtime.Versioning;

...    

object[] list = Assembly.GetExecutingAssembly().GetCustomAttributes(true);
var attribute = list.OfType<TargetFrameworkAttribute>().First();

Console.WriteLine(attribute.FrameworkName);
Console.WriteLine(attribute.FrameworkDisplayName);

Will return

a.FrameworkName ".NETFramework,Version=v4.0"    string
a.FrameworkDisplayName  ".NET Framework 4"      string

a.FrameworkName ".NETFramework,Version=v4.5"    string
a.FrameworkDisplayName  ".NET Framework 4.5"    string

a.FrameworkName ".NETFramework,Version=v4.5.1"  string
a.FrameworkDisplayName  ".NET Framework 4.5.1"  string

Solution 3:

class Program {
  static void Main(string[] args) { 
      System.Console.WriteLine(
             System.Reflection.Assembly.LoadFrom(args[0]).ImageRuntimeVersion);
  }
}

Compile and run the above application under the latest .NET Framework (as an older CLR may be unable to load assemblies requiring a newer CLR) and run it passing the path to the assembly you want to check as the command line argument.