Thursday, October 14, 2021

[.NET 6] Implement custom LogProvider with RabbitMQ into ILogger

In .NET 6, ILogger is very easy to use, but on modern project, we will write log to somewhere else and use log viewer to read it. For example: sent log to RabbitMQ and read on Kibana

Here is a demo to show how to lmplement a custom logging provider with RabbitMQ into ILogger in .NET 6 RC1, basically same as this article but with some modify.

Step 0 : Before Start

In this demo we choose RabbitMQ.Client to communite with RabbitMQ, you can choose other client if you want, just install it from nuget, easy.

Another thing is RabbitMQ server, if you don't have one, you can use docker to create one.

docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3.9-management

Tuesday, September 28, 2021

[.NET 6] System.StackOverflowException after upgrade VS2022 to Preview 4.1 from 3.1

After upgrade VS2022 to Preview 4.1 from 3.1, my project throw StackOverflowException (after fix lots of reference error)
  Message=Exception of type 'System.StackOverflowException' was thrown.

Stack overflow.
Repeat 2291 times:
   at Microsoft.Extensions.Primitives.ChangeToken+ChangeTokenRegistration`1[[System.__Canon, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].OnChangeTokenFired()
   at Microsoft.Extensions.Primitives.ChangeToken+ChangeTokenRegistration`1+<>c[[System.__Canon, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<RegisterChangeTokenCallback>b__7_0(System.Object)
   at System.Threading.CancellationTokenSource.Invoke(System.Delegate, System.Object, System.Threading.CancellationTokenSource)
   at System.Threading.CancellationTokenSource.Register(System.Delegate, System.Object, System.Threading.SynchronizationContext, System.Threading.ExecutionContext)
   at System.Threading.CancellationToken.Register(System.Delegate, System.Object, Boolean, Boolean)
   at System.Threading.CancellationToken.Register(System.Action`1<System.Object>, System.Object)
   at Microsoft.Extensions.Configuration.ConfigurationReloadToken.RegisterChangeCallback(System.Action`1<System.Object>, System.Object)
   at Microsoft.Extensions.Primitives.ChangeToken+ChangeTokenRegistration`1[[System.__Canon, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].RegisterChangeTokenCallback(Microsoft.Extensions.Primitives.IChangeToken)
   at Microsoft.Extensions.Primitives.ChangeToken+ChangeTokenRegistration`1[[System.__Canon, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].OnChangeTokenFired()
   at Microsoft.Extensions.Primitives.ChangeToken+ChangeTokenRegistration`1+<>c[[System.__Canon, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<RegisterChangeTokenCallback>b__7_0(System.Object)
   at System.Threading.CancellationTokenSource.Invoke(System.Delegate, System.Object, System.Threading.CancellationTokenSource)
   at System.Threading.CancellationTokenSource+CallbackNode+<>c.<ExecuteCallback>b__9_0(System.Object)
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Threading.CancellationTokenSource+CallbackNode.ExecuteCallback()
   at System.Threading.CancellationTokenSource.ExecuteCallbackHandlers(Boolean)
   at System.Threading.CancellationTokenSource.NotifyCancellation(Boolean)
   at System.Threading.CancellationTokenSource.Cancel()
   at Microsoft.Extensions.Configuration.ConfigurationManager.RaiseChanged()
   at Microsoft.Extensions.Configuration.ConfigurationManager.AddSource(Microsoft.Extensions.Configuration.IConfigurationSource)
   at Microsoft.Extensions.Configuration.ConfigurationManager.Microsoft.Extensions.Configuration.IConfigurationBuilder.Add(Microsoft.Extensions.Configuration.IConfigurationSource)
   at Microsoft.Extensions.Configuration.ChainedBuilderExtensions.AddConfiguration(Microsoft.Extensions.Configuration.IConfigurationBuilder, Microsoft.Extensions.Configuration.IConfiguration, Boolean)
   at Microsoft.Extensions.Configuration.ChainedBuilderExtensions.AddConfiguration(Microsoft.Extensions.Configuration.IConfigurationBuilder, Microsoft.Extensions.Configuration.IConfiguration)
   at Microsoft.AspNetCore.Builder.WebApplicationBuilder.Build()
   at Program.<Main>$(System.String[])

I know post to MS's developer forum is useless, and VS2022 can't downgrade now, so the only way is try and error by myself.

Turn out, the stackoverflow exception cause by Microsoft.Extensions.Configuration from this code:
After more dig-in, I found the framework already called this on Hosting , so maybe the duplicate call cause the stackoverflow exception, but still not sure why it worked on VS2022 preview 3.1, not work on preview 4.1.


Remove the line
(or similar) on your Program.cs

Wednesday, September 22, 2021

[JAVA] HMAC SHA384 example code

It was a bit hard to find correct HMAC SHA384 code for JAVA, so here to share my example code, hope can save some time to try and error.

import javax.crypto.spec.SecretKeySpec;
import javax.crypto.Mac;

public class SecureUtils {

private static String bytesToHex(final byte[] hash) {
    final StringBuffer hexString = new StringBuffer();
    for (int i = 0; i < hash.length; i++) {
        final String hex = Integer.toHexString(0xff & hash[i]);
        if (hex.length() == 1) {
    return hexString.toString();

public static void main(String[] args) throws NoSuchAlgorithmException {
    final String nonce = "test"; //your key
    final String message = "Password"; //your plain txt
    SecretKeySpec signingKey = new SecretKeySpec(nonce.getBytes(),"HmacSHA384");
    final Mac mac = Mac.getInstance("HmacSHA384");
        catch(Exception ex){    }

You can test this example in here 

Check result with online hmac generator

Those code modify from stackoverflow HMAC SHA-384 in Java

Sunday, January 31, 2021

[敗家] Alienware m17 R3

Alienware m17 R3

上一台筆電是2013年買的Alienware M14x R2,拿來寫code已經有點慢了,最近終於找了機會買了新筆電,17吋螢幕真的比較適用啊。




Sunday, November 8, 2020

[.NET Core] 400 Bad Request / 'MS-ASPNETCORE-TOKEN' does not match the expected pairing token

At this time, I am testing an old code build by .NET Core 2.0, when I tring to send request to the service, I always got 400 Bad Request, but I can know the service got request because I am running debug mode, it shows request coming and exception happend.

Since I can't find out the error just by 400 bad request, I open "Application Insights Search" in Visual Studio and found this error.

After some digging on stackoverflow, I found the error cause by a old version bug.

This question "Cannot debug in Visual Studio after changing the port number?" 's answer has good explain about this error.

You are getting this error message because Kestrel expected to run behind IIS, and received a direct request. And it noticed that because IIS was not there to inject the MS-ASPNETCORE-TOKEN header. --Gerardo Grignoli

Here have some options to solve the problem:

  1. Call UseUrls() before UseIISIntegration() 
  2. Use Kestrel to debug, not IIS Express 
  3. Upgrade the framework

That's all,

Sunday, November 1, 2020

[.NET core] Localization with Enumeration

In .NET core, doing i18n is more easy than .NET Framework in my opinions, just give appropriate setting, then you can easily assign i18n string to anyplace you want.

Let's see how it work.

1.Add resource file 

Usually I will put my resource file in [Resources] folder, remember put cultureInfo name on resx file like this.

2.Setup Startup.cs

Add following code (depending how many language you support) into your IServiceCollection
//set Support Cultures and default
services.Configure(options =>
    var supportedCultures = new[]{
        new CultureInfo("en-US"),
        new CultureInfo("zh-TW"),
        new CultureInfo("ja-JP")
    options.DefaultRequestCulture = new RequestCulture("en-US");
    options.SupportedCultures = supportedCultures;
    options.SupportedUICultures = supportedCultures;
//set resource path
services.AddLocalization(options => options.ResourcesPath = "Resources");

Make sure your ResourcesPath set to right path.

3.DI Localizer

Since we are using .NET Core, so we need to DI our Localizer before we using it, for example if you are use it on a controller.
private readonly IStringLocalizer _localizer;
public YourController(IStringLocalizerFactory factory)
   _localizer = factory.Create("Message", System.Reflection.Assembly.GetExecutingAssembly().GetName().Name);

The "Message" is my resource name, you can DI multi Localizer if you have not only one resource group.


Here is the content of my resource, the usage for Localizer is easy, just use it like a dictionary.
var str = _localizer["Cool"];

If you wanna get a localization string for enum, it was easy too, for example your enum called "WeatherSummary".
var str = _localizer[WeatherSummary.Cool.ToString()];

It was very simple, don't need add custom thing like LocalizedDescriptionAttribute for enum i18n in .NET Framework.

You can check my demo code on github .NET-Core-Localization-and-Enum

Hope you enjoy it.

Sunday, October 25, 2020

[.NET core] System.NotSupportedException: The collection type 'System.Object' on 'somewhere' is not supported.

Somehow if you are using .NET core and return a object on controller, you might meet this exception.

  System.NotSupportedException: The collection type 'System.Object' on 'somewhere.InnerResult.Data' is not supported.
   at System.Text.Json.JsonPropertyInfoNotNullable`4.GetDictionaryKeyAndValueFromGenericDictionary(WriteStackFrame& writeStackFrame, String& key, Object& value)
   at System.Text.Json.JsonPropertyInfo.GetDictionaryKeyAndValue(WriteStackFrame& writeStackFrame, String& key, Object& value)
   at System.Text.Json.JsonSerializer.HandleDictionary(JsonClassInfo elementClassInfo, JsonSerializerOptions options, Utf8JsonWriter writer, WriteStack& state)
   at System.Text.Json.JsonSerializer.Write(Utf8JsonWriter writer, Int32 originalWriterDepth, Int32 flushThreshold, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteCore(Utf8JsonWriter writer, Object value, Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.WriteCore(PooledByteBufferWriter output, Object value, Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.WriteCoreString(Object value, Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.Serialize[TValue](TValue value, JsonSerializerOptions options)
   at TestWeb.Controllers.AuthController.VerifyToken(String token, Int32 tp) in C:\repos\somewhere\TestWeb\Controllers\AuthController.cs:line 51

In this project, I always return my custom result called InnerResult in API controller.
    public class InnerResult
        public bool Success { get; set; } = true;
        public int Code { get; set; }
        public string Message { get; set; }
        public dynamic Data { get; set; }

If the result json was this format, .NET core default can handle it.
    "success": true,
    "code": 0,
    "message": null,
    "data": "vfu3MF5RFlQV9dWNQCFh6iRPNxeezFaV"

but if some object in property, it will throw System.NotSupportedException

    "success": true,
    "code": 0,
    "message": null,
    "data": {
        "name": "Died"

That's because in .NET core , they default using System.Text.Json to deal with json convert, but somehow it can't handle object in property, so......

To solve it, we can use our old friend Json.NET to save the day. (actually, using Microsoft.AspNetCore.Mvc.NewtonsoftJson)

Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson -Version 3.1.9

If you are using .NET core 2.x , add .AddNewtonsoftJson() after your AddMVC()


If using .NET core 3.x , add it after what you have.


Then no more this System.NotSupportedExceptio again.

Sunday, October 18, 2020

[.NET core] AddPolicy to Authorize on MVC controller

Sometimes when you are using C# identity, the [Authorize] attribute is not enough,for example, you want additional check not only claims or role, then you can try add policy to make it. 

In this example, we assume a part of method need check token in user claims before access, here is how to implement it. 

1.add a AuthorizationHandler for your policy 
namespace Example.Handler
    // Custom AuthorizationHandler for check token in claim
    public class AuthorizeTokenHandler : AuthorizationHandler<TokenRequirement>
        private readonly AuthService _auth;

        public AuthorizeTokenHandler(AuthService auth)
            _auth = auth;
        protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, TokenRequirement requirement)
            //no token claim
            if (!context.User.HasClaim(x => x.Type == "Token"))
                return Task.CompletedTask;

            var username = context.User.FindFirst(ClaimTypes.Name).Value;
            var token = context.User.FindFirst("Token").Value;

            #region check token
            if (_auth.CheckToken(username,token))

            return Task.CompletedTask;

    public class TokenRequirement : IAuthorizationRequirement

2. add to startup, in ConfigureServices

            services.AddSingleton<IAuthorizationHandler, AuthorizeTokenHandler>();
            //add policy
            services.AddAuthorization(options =>
                options.AddPolicy("TokenRequire", policy =>
                    policy.Requirements.Add(new TokenRequirement()));

3. apply policy to Authorize when you need

[Authorize(Policy = "TokenRequire")]
public ApiResult SomeMethod()

That's all, enjoy it.

Sunday, October 11, 2020

[C#] Best Practices of Get Claim from Identity

If you are using ASP.NET Identity, whatever using ASP.NET Core Identy or ASP.NET Identity, usually you will add some claims into the identity and use it later, but I saw lot people using unsafe way to get claim value from identity, it may cause uncatch error if the claim type not exists, let's see the code.
//set some claims first
var claims = new List<Claim>
     new Claim(ClaimTypes.Name,"test name"),
     new Claim("Token","token123"),
     new Claim("Number","3")
     //new Claim("dummy","dummy string")
var ci = new ClaimsIdentity(claims);

//most seen way, throw error if not exists
var name = ci.Claims.First(x => x.Type == ClaimTypes.Name).Value;
var token = ci.Claims.First(x => x.Type == "Token").Value;  
//using FirstOrDefault() only, throw error if not exists
//var dunno = ci.Claims.FirstOrDefault(x => x.Type == "dunno").Value;

Using this way is easy, but if the claim not exists, if will cause error, whatever you are using First() or FirstOrDefault(). If want to using FirstOrDefault() to get claim value, you can using this fixed way.

            //fixed FirstOrDefault way: return null if not exists
            var dunno = ci.Claims.Where(x => x.Type == "dunno").Select(x => x.Value).FirstOrDefault();

but you can use HasClaim method to check claim exist first, and give a proper value if it not exists.

            //safe way: using HasClaim to check
            var dummy = ci.HasClaim(x => x.Type == "dummy")
                ? ci.Claims.First(x => x.Type == "dummy").Value
                : null;

or you can choose this short way by using FindFirst method.

            //short way: using FindFirst
            var dummyShort = ci.FindFirst("dummy")?.Value;
            //short way for int
            int.TryParse(ci.FindFirst("Number")?.Value, out var number);

I think use ClaimsIdentity.FindFirst Method is the best practices for get claim value.
You can test those here in here

Tuesday, June 2, 2020



以下資料來源翻譯自Yellowstone Bear World


Myth #1: Bears have bad eyesight


Bears actually have excellent eyesight.

就像您家的狗或貓一樣,熊擁有出色的夜視能力。 牠們的眼睛後部有一個稱為脈絡膜層(Tapetum lucidum)的反射膜,該膜可反射光,並使光敏細胞對光進行第二次反應,從而極大地增強了他們在夜間的視力。


因此,別被騙了...那些熊可能會在您見到牠們之前先見到您! (有關資訊請參見Sylvia Dolson的《熊學 Bear-ology》)