Determine framework (CLR) version of assembly

Question

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

Answer 1

As @mistika suggested, it is better to use ReflectionOnlyLoadFrom() rather than LoadFrom(). The downside of this is that calling GetCustomAttributes() on an assembly loaded with ReflectionOnlyLoadFrom() throws an exception. You need to call GetCustomAttributesData() instead:

var assembly = Assembly.ReflectionOnlyLoadFrom(assemblyPath);
var customAttributes = assembly.GetCustomAttributesData();
var targetFramework = customAttributes.FirstOrDefault(attr => attr.AttributeType.Equals(typeof(TargetFrameworkAttribute)));

var frameworkName = string.Empty;
var frameworkDisplayName = string.Empty;
if (null != targetFramework)
{
    if(targetFramework.ConstructorArguments.Any())
    {
        // first argument is the name of the framework.
        frameworkName = (string)targetFramework.ConstructorArguments[0].Value;
    }

    // search for a named argument called "FrameworkDisplayName"
    var frameworkDisplayNameArg = targetFramework.NamedArguments.FirstOrDefault(arg => arg.MemberName.Equals("FrameworkDisplayName"));
    if (null != frameworkDisplayNameArg)
    {
        frameworkDisplayName = (string)frameworkDisplayNameArg.TypedValue.Value;
    }
}

Console.WriteLine("Framework Name: " + frameworkName);
Console.WriteLine("Framework Display Name: " + frameworkDisplayName);