Introduction

The PublicKeyToken is part of a strong-named .NET assembly's identity. It helps the runtime distinguish one signed assembly from another during binding. The important caveat is that not every DLL has a PublicKeyToken. If the assembly is not strong-named, the token is absent.

What the PublicKeyToken Represents

A .NET assembly identity typically includes:

• simple name
• version
• culture
• public key token

The token is a compact identifier derived from the assembly's full public key. You see it in binding redirects, AssemblyName, and FullName strings.

Example assembly identity:

MyLibrary, Version=1.2.3.4, Culture=neutral, PublicKeyToken=31bf3856ad364e35

If the DLL is unsigned, the token is usually null or missing.

Quickest CLI Method: sn.exe

If you have the .NET SDK or developer tools that include the strong-name utility, use:

sn -T MyLibrary.dll

That prints the public key token if the assembly is strong-named.

This is the fastest answer on machines where the tool is already available.

PowerShell Method Without sn.exe

PowerShell can read the assembly name directly.

$assemblyName = [System.Reflection.AssemblyName]::GetAssemblyName("C:\path\MyLibrary.dll")
$tokenBytes = $assemblyName.GetPublicKeyToken()
($tokenBytes | ForEach-Object { $_.ToString("x2") }) -join ""

Why this is useful:

• no need to locate sn.exe
• works well in automation scripts
• reads the token from the assembly metadata directly

If the result is empty, the DLL probably is not strong-named.

Small C# Programmatic Example

If you need the token in application code, use AssemblyName.

1using System;
2using System.Linq;
3using System.Reflection;
4
5class Program
6{
7    static void Main()
8    {
9        var name = AssemblyName.GetAssemblyName("MyLibrary.dll");
10        var token = name.GetPublicKeyToken();
11        var text = token == null || token.Length == 0
12            ? "null"
13            : string.Concat(token.Select(b => b.ToString("x2")));
14
15        Console.WriteLine(text);
16    }
17}

This is useful when writing diagnostics or tooling around assembly loading.

If the DLL Is Already Loaded

When the assembly is already loaded in a process, you can inspect its full name directly:

1using System;
2using System.Reflection;
3
4class Program
5{
6    static void Main()
7    {
8        Assembly asm = typeof(string).Assembly;
9        Console.WriteLine(asm.FullName);
10    }
11}

The FullName output includes the PublicKeyToken when present.

How to Interpret a Missing Token

A missing token does not necessarily mean the DLL is broken. It usually means the assembly was not strong-name signed.

That matters because:

• unsigned assemblies do not participate in strong-name identity the same way
• binding redirects that mention a token are only relevant for signed assemblies
• the Global Assembly Cache historically relied on strong naming

So if you are troubleshooting assembly binding, first confirm whether the DLL is even expected to have a token.

When This Matters in Practice

You usually need the token when:

• writing or debugging binding redirects
• comparing two copies of a DLL with similar names
• inspecting references in legacy .NET Framework apps
• diagnosing load failures involving assembly identity mismatches

If the problem is only "which file is this," then name and version may already be enough. The token matters when strong-name identity is part of the equation.

Common Pitfalls

• Expecting every DLL to have a PublicKeyToken even when it is unsigned.
• Reading the assembly file name and assuming it reveals signing details.
• Using sn.exe on a machine where the tool is not installed and concluding the DLL has no token.
• Forgetting that Assembly.FullName already exposes the token for loaded assemblies.
• Treating a missing token as an application bug instead of a signing choice.

Summary

• A PublicKeyToken exists only for strong-named assemblies.
• 'sn -T MyLibrary.dll is the fastest command-line method when available.'
• PowerShell and AssemblyName.GetAssemblyName() work well without sn.exe.
• 'Assembly.FullName shows the token for assemblies already loaded in memory.'
• If the token is missing, the DLL is usually unsigned rather than malformed.