Can't Access Azure Key Vault from desktop console app

I am having trouble accessing a secret from an Azure key vault. I suspect the problem is that I don't adequately understand the terminology, so the arguments I'm supplying to various API calls are wrong.

Here's the basic code I'm using:

    protected async Task<string> GetCommunityKeyAsync( UserConfiguration user )
    {
        var client = new KeyVaultClient( 
            new KeyVaultClient.AuthenticationCallback( GetAccessTokenAsync ),
            new HttpClient() );

        // user.VaultUrl is the address of my key vault
        // e.g., https://previously-created-vault.vault.azure.net
        var secret = await client.GetSecretAsync( user.VaultUrl, "key-to-vault-created-in-azure-portal" );

        return secret.Value;
    }

    private async Task<string> GetAccessTokenAsync( string authority, string resource, string scope )
    {
        var context = new AuthenticationContext( authority, TokenCache.DefaultShared );

        // this line throws a "cannot identify user exception; see
        // below for details
        var result =
            await context.AcquireTokenAsync( resource, "id-of-app-registered-via-azure-portal", new UserCredential() );

        return result.AccessToken;
    }

Here is the exception that gets thrown:

Microsoft.IdentityModel.Clients.ActiveDirectory.AdalException
HResult=0x80131500 Message=unknown_user: Could not identify logged in user Source=Microsoft.IdentityModel.Clients.ActiveDirectory
StackTrace: at Microsoft.IdentityModel.Clients.ActiveDirectory.AcquireTokenNonInteractiveHandler.d__4.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.IdentityModel.Clients.ActiveDirectory.AcquireTokenHandlerBase.d__57.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.d__37.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContextIntegratedAuthExtensions.d__0.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter1.GetResult() at NextDoorScanner.ScannerJob.<GetAccessTokenAsync>d__21.MoveNext() in C:\Programming\CommunityScanner\CommunityScanner\ScannerJob.cs:line 197 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult() at Microsoft.Azure.KeyVault.KeyVaultCredential.d__9.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult() at Microsoft.Azure.KeyVault.KeyVaultCredential.<ProcessHttpRequestAsync>d__10.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Azure.KeyVault.KeyVaultClient.<GetSecretWithHttpMessagesAsync>d__65.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult() at Microsoft.Azure.KeyVault.KeyVaultClientExtensions.d__11.MoveNext() at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter1.GetResult() at NextDoorScanner.ScannerJob.<GetCommunityKeyAsync>d__20.MoveNext() in C:\Programming\CommunityScanner\CommunityScanner\ScannerJob.cs:line 188 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter1.GetResult() at NextDoorScanner.NextDoorScannerJob.d__4.MoveNext() in C:\Programming\CommunityScanner\CommunityScanner\NextDoorScannerJob.cs:line 46 at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() at NextDoorScanner.Program.Main(String[] args) in C:\Programming\CommunityScanner\CommunityScanner\Program.cs:line 22

I did some configuration, I thought involving registering my desktop as an Azure user, via powershell:

Login-AzureRmAccount
// as I recall, this next line complained about the app ID already being   defined
New-AzureRmADServicePrincipal -ApplicationId 'id-of-app-previously-defined-via-azure-portal'
Set-AzureRmKeyVaultAccessPolicy -VaultName 'vault-name' -ServicePrincipalName id-of-app-previously-defined-via-azure-portal -PermissionsToSecrets Get

I'm unclear if I'm supposed to be providing the vault key to GetSecretAsync(). I also wonder if I'm supposed to be doing something other than passing a newly-created UserCredential to AcquireTokenAsync(). Finally, I see references online to creating a storage account for use with key vaults, which I did, but I didn't create the vault I'm using "in" a storage account. And I'm not identifying the storage account in the code.

Help, or a reference to a really good example accessing key vaults from a console desktop app would be appreciated.

Mark's blog was extremely helpful, from that blog I learnt how to do it and below are the steps and code as of 6-Nov-2018.

Summary of the steps:

1. Register App
2. Create Key inside this newly registered App
3. Create Key Vault and Assign permission to the app
4. Create Secret inside the vault

Access them thru code

using Microsoft.Azure.KeyVault;
using Microsoft.IdentityModel.Clients.ActiveDirectory;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

namespace Experiments.AzureKeyValut
{
    internal class AzureKeyValueDemo
    {
        private static async Task Main(string[] args)
        {
            await GetSecretAsync("https://YOURVAULTNAME.vault.azure.net/", "YourSecretKey");
        }

        private static async Task<string> GetSecretAsync(string vaultUrl, string vaultKey)
        {
            var client = new KeyVaultClient(new KeyVaultClient.AuthenticationCallback(GetAccessTokenAsync), new HttpClient());
            var secret = await client.GetSecretAsync(vaultUrl, vaultKey);

            return secret.Value;
        }

        private static async Task<string> GetAccessTokenAsync(string authority, string resource, string scope)
        {
            //DEMO ONLY
            //Storing ApplicationId and Key in code is bad idea :)
            var appCredentials = new ClientCredential("YourApplicationId", "YourApplicationKey");
            var context = new AuthenticationContext(authority, TokenCache.DefaultShared);

            var result = await context.AcquireTokenAsync(resource, appCredentials);

            return result.AccessToken;
        }
    }
}

How to register your app:

How to create Azure App's password and get your App's Id

How to create Azure Key Vault and Assign Permissions

How to create Azure secrets

How to access it thru code