Category: .NET Core

Country Tag Helper–part 5

Now the Country Tag Helper supports .NET Standard 2.0 . This means that support .NET Core 2.0 .

Also, I have made a NuGET package in order to install on every .NET Core 2.0 application with explanations: 

The only trouble here was to add references and make documentation in VS2017 about package ( see )

As I said , the source is at GitHub and demo at

What remains to be done:

add select2 with image flags   

provider / dependency injection for FromIP / wiki on github

Country Tag Helper–part 4


Now I want to see somewhere in order to prove it Ii s right. I choose because it is free – and can not beat free for free source.

I made github integration and modify the .csproj file accordingly to 

The result is at 

Also , I have to modify the code source to get the ip of the user :

string GetUserIP(ViewContext vc)
            StringValues headerFwd;
            if (ViewContext.HttpContext?.Request?.Headers?.TryGetValue("X-Forwarded-For", out headerFwd) ?? false)
                string rawValues = headerFwd.ToString();
                if (!string.IsNullOrWhiteSpace(rawValues))
                    return rawValues.Split(',')[0];

            return ViewContext.HttpContext?.Connection?.RemoteIpAddress?.ToString();


where ViewContext is

        public ViewContext ViewContext { get; set; }

Country Tag Helper – part 3

Adding empty item – easy peasy. Just append "<option selected style=’display: none’ value=”></option>";


if (ASPCountryEmpty)
                    string empty = "<option selected style='display: none' value=''></option>";

For getting the IP, I was trying to balance the 2 variants: downloading GeoIP database ( or calling .

I do call – and the next point is to use Dependency Injection … or a provider to do that.

For the moment, the code is:

 private async Task<string> GetCountryCodeFromIP(string ip)
            //ip= "";
            var url = ""+ip;
            var request = WebRequest.Create(url);
            request.Method = "GET";
            using (var wr = await request.GetResponseAsync())
                using (var receiveStream = wr.GetResponseStream())
                    using (var reader = new StreamReader(receiveStream, Encoding.UTF8))
                        string content = reader.ReadToEnd();
                        return content.Split(',')[1];


CountryTagHelper–part 2

Finally, I have arrived at functionality. I said that I want something like

<select asp-country="true" asp-country-selected="US" >


The functionality is very easy to be added:

The entire class is :

using Microsoft.AspNetCore.Razor.TagHelpers;
using Microsoft.Extensions.Localization;
using System;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;

namespace CTHWeb.Controllers
    [HtmlTargetElement("select", Attributes = ASPCountryAttributeName)]
    public class CountryTagHelper:TagHelper
        private const string ASPCountryAttributeName = "asp-country";
        private const string ASPCountrySelectedAttributeName = "asp-country-selected";

        public bool ASPCountry { get; set; }

        public string ASPCountrySelected{ get; set; }

        static string[] CountryISO;
        //static PropertyInfo[] properties;
        static CountryTagHelper()
            var t =typeof( ResCTH);
            var properties= t.GetProperties(
                BindingFlags.Public |
                BindingFlags.Static |
            CountryISO = properties
                .Select(it => it.Name)
        public override Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
            if (ASPCountry)
                bool existSelected = !string.IsNullOrWhiteSpace(ASPCountrySelected);
                string option = "<option value='{0}' {2}>{1}</option>";
                foreach (var item in CountryISO)
                    string selected = "";
                    string localizedName = ResCTH.ResourceManager.GetString(item);
                    if (existSelected)
                        bool currentItem = string.Equals(item, ASPCountrySelected, StringComparison.CurrentCultureIgnoreCase);
                        currentItem = currentItem || string.Equals(localizedName, ASPCountrySelected, StringComparison.CurrentCultureIgnoreCase);
                        if (currentItem)
                            selected = "selected";
                    output.Content.AppendFormat(option, item, localizedName,selected);
            return base.ProcessAsync(context, output);


The important thing is that it works with other html attributes, like

<select asp-country="true" asp-country-selected="US" disabled=”disabled”>


What it remains to be done:

  1. from IP – recognize the country of the visitor from IP
  2. localized – display messages in other language
  3. first item empty – now it selects Andorra
  4. Add select2 with image flags
  5. NuGet package
  6. / wiki on github
  7. tests

Country tag helper–part 1


What I want to do is to create a Country Tag Helper for core.

Something like

<select asp-country=”true”

and then list all countries in this select. More, it should be localized ( Germany vs Allemagne). That means 1 or more resource files 


First I need initial data: The WorldBank API gives us the names and I have made a project that inspects that API.

To retrieve data in resource format , it is simple:

 var r = new CountriesRepository();
            var arr = r.GetCountries().Result.
                Select(it =>
                $"<data name = \"{it.iso2Code}\" xml:space=\"preserve\" >" +

                $"<value>{}</value>" +
            var s = string.Join(Environment.NewLine, arr);
            File.WriteAllText(@"D:\c.txt", s);


Then we could copy paste into resources:

 <data name = "AW" xml:space="preserve" ><value>Aruba</value></data>
  <data name = "AF" xml:space="preserve" ><value>Afghanistan</value></data>
  <data name = "AO" xml:space="preserve" ><value>Angola</value></data>


Now I want to make a list of those names – so I need this code to translate between C# generated code from resource

public static string AD {
            get {
                return ResourceManager.GetString("AD", resourceCulture);
public static string AE {
            get {
                return ResourceManager.GetString("AE", resourceCulture);


and a list of names to be put into select.

Reflection to the rescue:

  var t =typeof( ResCTH);
            properties= t.GetProperties(
                BindingFlags.Public |
                BindingFlags.Static |
            CountryISO = properties
                .Select(it => it.Name)


The code is on github and I will improve next time.

Making any call to a function of an object thread safe



I was wondering how to modify old code to support threads /task .

So I was making a small project about making any function of an object thread safe.

NuGet Package at :

The solution contain tests and 2 console project for .NET Core and .NET Framework 4.5.1

The usage is pretty easy

Let’s say you have this

Calculation c = new Calculation();

And you want


to be thread safe

In the Package Manager Console write:

Install-Package ThreadSafeObject

Then modify your code to:

Calculation c = new Calculation();
dynamic ts = new ThreadSafe(c);

It is a toy project- however, it has tests to prove it is correct.

You can download the code source from

InternalsVisibleTo usage

I do not know if you know  InternalsVisibleToAttribute  .

I have used on a project , that deals with World Bank API to get information

Let’s take an example: Countries:

I have had a class CountriesRepository, that deals with transforming countries Json from WorldBank to Country classes. How can I test it WITHOUT relying on reading data from the internet ?


1. Make an interface to grab JSON , IJSonData

    public interface IJsonData
        Task<string> JsonData(int page = 1);

2. Make a class JSONCountry that reads JSON from HTTP and implements IJSonData

3.  Make the CountryRepository class with 2 constructors  – one with IJSonData and the default calling JSONCountry

[assembly: InternalsVisibleTo("WorldBank.Test")]
namespace WorldBank.Repository
    public class CountriesRepository
        private IJsonData data;
        public CountriesRepository():this(new JsonCountries())

//this is internal - could not see by outside projects with exception of WorldBank.Test
//see InternalsVisibleTo above
        internal CountriesRepository(IJsonData data)
   = data;

Optional: when testing manually, save the json into same files on the hard disk – you will need for point 5

4. The code that will use CountryRepository in official way will use the default – will not see the one with IJSonData

var c = new CountriesRepository();
var data = c.GetCountries().Result;

5. The testing code will define another class JSONFromHard that implements IJSonData and reads data from Hard

class JsonFromHard : IJsonData
//code to read files from disk 
// you have saved those when testing manually 
//see point 2 the optional part 

6. Because I have defined InternalsVisibleToAttribute to the WorldBank.Test, the Test dll can see the constructor with IJSonData  and then it class with JSONFromHard   – and I have no dependecy on the Http


public void GetAndInterpretData()
            //uses [assembly: InternalsVisibleTo("WorldBank.Test")]
            var c = new CountriesRepository(new JsonFromHard("Countries"));
            var data = c.GetCountries().Result;
            Assert.Equal(218, data.Length);

You can download the project from  to see working.

ImageTagHelper in .NET Core–add data URI scheme

The ImageTagHelper in ASP.NET Core MVC ( is lacking one attribute that I find somehow useful: a data uri to embed the image as base64 ( )

I was curious about how fast it will be to make such a modification on my PC.

So the process was:

  1. Downloading branch rel/1.1.1 from as a zip file
  2. Unlock the file, unpack, run  MVC.sln with VS2015
  3. Compile the entire project.
  4. See tests  ( also run dotnet test in the Mvc-rel-1.1.1\test\Microsoft.AspNetCore.Mvc.TagHelpers.Test to figure what was missing)
  5. Started modifying the file ImageTagHelper( adding
     public bool RenderBase64 

    and creating FileBase64ContentProvider.cs with the (approximately) same content as FileVersionProvider

  6. Adding tests to  mvc-rel-1.1.1\test\microsoft.aspnetcore.mvc.taghelpers.test\imagetaghelpertest.cs  ( also modifying mocker –
    for my purposes, to read the file, I need file length

                    .Setup(m => m.CreateReadStream())                
                    .Returns(() => new MemoryStream(Encoding.UTF8.GetBytes("Hello World!")));
    mockFile.SetupGet(f => f.Length).Returns(12);
  7. Modifying HtmlTargetElement attribute from ImageTagHelper
  8. Adding “Microsoft.AspNetCore.StaticFiles”: “1.1.0”, and app.UseStaticFiles();  to HtmlGenerationWebSite and going to http://localhost:5551/HtmlGeneration_Home/image

And that was all. Now I will see how to fork and submit changes 😉

Later Edit: Submit a bug, fork, pull request. Approved.

ASP.NET Core and Windows Authentication

Just a reminder of how to configure ASP.NET Core and Windows Authentication

1. Configure IIS

2. Go to properties folder, file launchSettings.json and modify

"iisSettings": {     "windowsAuthentication": true,     "anonymousAuthentication": false,    //other data

3. When you compile and run , the Web.Config will be modified for forwardWindowsAuthToken :

<aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" forwardWindowsAuthToken="true" stdoutLogEnabled="false" />