ng g c core/bread-crumb

import { BreadCrumbComponent } from "./bread-crumb/bread-crumb.component";

@NgModule({
  imports: [CommonModule, RouterModule],
  exports: [
    // components that are used in app.component.ts will be listed here.
    BreadCrumbComponent
  ],
  declarations: [
    // components that are used in app.component.ts will be listed here.
    BreadCrumbComponent
  ]
})
export class CoreModule {}

export interface BreadCrumb {
  label: string;
  url: string;
};

import { Component, OnInit, ViewEncapsulation } from "@angular/core";
import { ActivatedRoute, NavigationEnd, Router } from "@angular/router";
import { BreadCrumb } from "./bread-crumb";
import { Observable } from "rxjs/Observable";

@Component({
  selector: "app-bread-crumb",
  templateUrl: "./bread-crumb.component.html",
  styleUrls: ["./bread-crumb.component.css"],
  encapsulation: ViewEncapsulation.None
})
export class BreadCrumbComponent implements OnInit {

  breadcrumbs$: Observable<BreadCrumb[]>;

  constructor(private activatedRoute: ActivatedRoute, private router: Router) { }

  ngOnInit() {
    this.breadcrumbs$ = this.router.events
      .filter(event => event instanceof NavigationEnd)
      .distinctUntilChanged()
      .map(event => event ? this.buildBreadCrumbs(this.activatedRoute.root) : []);
  }

  buildBreadCrumbs(route: ActivatedRoute, url: string = "", breadcrumbs: Array<BreadCrumb> = []): Array<BreadCrumb> {
    const routeDataBreadCrumbKey = "breadcrumb";
    const routeConfig = route.routeConfig;
    const path = routeConfig && routeConfig.path !== undefined ? routeConfig.path : "";

    let label = path;
    if (url === "") {
      label = "Home";
    } else if (routeConfig && routeConfig.data !== undefined) {
      label = routeConfig.data[routeDataBreadCrumbKey];
    }

    const nextUrl = `${url}${path}/`;
    const breadcrumb: BreadCrumb = {
      label: label,
      url: nextUrl
    };
    console.log("breadcrumb", { path: path, label: label, url: nextUrl, route: route });
    const newBreadcrumbs = [...breadcrumbs, breadcrumb];
    if (route.firstChild) {
      return this.buildBreadCrumbs(route.firstChild, nextUrl, newBreadcrumbs);
    }
    return newBreadcrumbs;
  }

}

  ngOnInit() {
    this.breadcrumbs$ = this.router.events
      .filter(event => event instanceof NavigationEnd)
      .distinctUntilChanged()
      .map(event => event ? this.buildBreadCrumbs(this.activatedRoute.root) : []);
  }

const routes: Routes = [
  {
    path: "breadCrumbTest",
    data: { breadcrumb: "Parent1" },
    children: [
      {
        path: "", component: Parent1Component
      },
      {
        path: "Parent1Child1",
        data: { breadcrumb: "Parent1-Child1" },
        children: [
          {
            path: "", component: Parent1Child1Component
          },
          {
            path: "Parent1Child1Child1", component: Parent1Child1Child1Component,
            data: { breadcrumb: "Parent1-Child1 Child1" }
          }
        ]
      }
    ]
  }
];

 data: { breadcrumb: "Parent1-Child1 Child1" }

  buildBreadCrumbs(route: ActivatedRoute, url: string = "", breadcrumbs: Array<BreadCrumb> = []): Array<BreadCrumb> {
    const routeDataBreadCrumbKey = "breadcrumb";
    const routeConfig = route.routeConfig;
    const path = routeConfig && routeConfig.path !== undefined ? routeConfig.path : "";

    let label = path;
    if (url === "") {
      label = "Home";
    } else if (routeConfig && routeConfig.data !== undefined) {
      label = routeConfig.data[routeDataBreadCrumbKey];
    }

    const nextUrl = `${url}${path}/`;
    const breadcrumb: BreadCrumb = {
      label: label,
      url: nextUrl
    };

    const newBreadcrumbs = [...breadcrumbs, breadcrumb];
    if (route.firstChild) {
      return this.buildBreadCrumbs(route.firstChild, nextUrl, newBreadcrumbs);
    }
    return newBreadcrumbs;

 encapsulation: ViewEncapsulation.None

<ol class="breadcrumb">
  <li *ngFor="let breadcrumb of breadcrumbs$ | async" class="breadcrumb-item">
    <a [routerLink]="[breadcrumb.url]">{{ breadcrumb.label }}</a>
  </li>
</ol>

   breadcrumbs$: Observable<BreadCrumb[]>;

<div class="container">
  <app-bread-crumb></app-bread-crumb>
  <router-outlet></router-outlet>
</div>

 This type of CollectionView does not support changes to its SourceCollection
from a thread different from the Dispatcher thread

 System.InvalidOperationException: This exception was thrown because the generator for control
'System.Windows.Controls.ListView Items.Count:62' with name '(unnamed)' has received sequence of
CollectionChanged events that do not agree with the current state of the Items collection.
The following differences were detected:  Accumulated count 61 is different from actual count 62.

 private static object _lock = new object();
//...
BindingOperations.EnableCollectionSynchronization(persons, _lock);

public static void EnableCollectionSynchronization(IEnumerable collection, object lockObject)
{
      MethodInfo method = typeof(BindingOperations).GetMethod("EnableCollectionSynchronization",
             new Type[] { typeof(IEnumerable), typeof(object) });
      if (method != null)
      {
         method.Invoke(null, new object[] { collection, lockObject });
      }
}

using System;
using System.Collections;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Linq;
using System.Windows.Data;
using System.Windows.Threading;

namespace WpfAsyncCollection
{
    public class AsyncObservableCollection<T> : ObservableCollection<T>
    {
        public override event NotifyCollectionChangedEventHandler CollectionChanged;
        private static object _syncLock = new object();

        public AsyncObservableCollection()
        {
            enableCollectionSynchronization(this, _syncLock);
        }

        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            using (BlockReentrancy())
            {
                var eh = CollectionChanged;
                if (eh == null) return;

                var dispatcher = (from NotifyCollectionChangedEventHandler nh in eh.GetInvocationList()
                                  let dpo = nh.Target as DispatcherObject
                                  where dpo != null
                                  select dpo.Dispatcher).FirstOrDefault();

                if (dispatcher != null && dispatcher.CheckAccess() == false)
                {
                    dispatcher.Invoke(DispatcherPriority.DataBind, (Action)(() => OnCollectionChanged(e)));
                }
                else
                {
                    foreach (NotifyCollectionChangedEventHandler nh in eh.GetInvocationList())
                        nh.Invoke(this, e);
                }
            }
        }

        private static void enableCollectionSynchronization(IEnumerable collection, object lockObject)
        {
            var method = typeof(BindingOperations).GetMethod("EnableCollectionSynchronization", 
                                    new Type[] { typeof(IEnumerable), typeof(object) });
            if (method != null)
            {
                // It's .NET 4.5
                method.Invoke(null, new object[] { collection, lockObject });
            }
        }
    }
}

 static T Add<T>(T left, T right) where T : INumber<T> => left + right;

public readonly struct Int32 : 
  IComparable, 
  IComparable<int>, 
  IConvertible, 
  IEquatable<int>, 
  IFormattable, 
  IParsable<int>, 
  ISpanFormattable, 
  ISpanParsable<int>, 
  IAdditionOperators<int, int, int>, 
  IAdditiveIdentity<int, int>, 
  IBinaryInteger<int>, 
  IBinaryNumber<int>, 
  IBitwiseOperators<int, int, int>, 
  IComparisonOperators<int, int, bool>, 
  IEqualityOperators<int, int, bool>, 
  IDecrementOperators<int>, 
  IDivisionOperators<int, int, int>, 
  IIncrementOperators<int>, 
  IModulusOperators<int, int, int>, 
  IMultiplicativeIdentity<int, int>, 
  IMultiplyOperators<int, int, int>, 
  INumber<int>, 
  INumberBase<int>, 
  ISubtractionOperators<int, int, int>, 
  IUnaryNegationOperators<int, int>, 
  IUnaryPlusOperators<int, int>, 
  IShiftOperators<int, int, int>, 
  IMinMaxValue<int>, 
  ISignedNumber<int>

public interface INumber<TSelf> : 
IComparable, 
IComparable<TSelf>, 
IEquatable<TSelf>, 
IFormattable, 
IParsable<TSelf>, 
ISpanFormattable, 
ISpanParsable<TSelf>, 
IAdditionOperators<TSelf, TSelf, TSelf>, 
IAdditiveIdentity<TSelf, TSelf>, 
IComparisonOperators<TSelf, TSelf, bool>, 
IEqualityOperators<TSelf, TSelf, bool>, 
IDecrementOperators<TSelf>, 
IDivisionOperators<TSelf, TSelf, TSelf>, 
IIncrementOperators<TSelf>, 
IModulusOperators<TSelf, TSelf, TSelf>, 
IMultiplicativeIdentity<TSelf, TSelf>, 
IMultiplyOperators<TSelf, TSelf, TSelf>, 
INumberBase<TSelf>, 
ISubtractionOperators<TSelf, TSelf, TSelf>, 
IUnaryNegationOperators<TSelf, TSelf>, 
IUnaryPlusOperators<TSelf, TSelf> where TSelf : INumber<TSelf>?

mkdir CSharpWithVSCode
cd CSharpWithVSCode
mkdir src
mkdir test
dotnet new sln

cd src
mkdir CSharpWithVSCode.ConsoleApp
cd CSharpWithVSCode.ConsoleApp
dotnet new console

cd..
cd..
cd src
mkdir CSharpWithVSCode.ClassLib
cd CSharpWithVSCode.ClassLib
dotnet new classlib

cd..
cd..
dotnet sln add .\src\CSharpWithVSCode.ConsoleApp\CSharpWithVSCode.ConsoleApp.csproj
dotnet sln add .\src\CSharpWithVSCode.ClassLib\CSharpWithVSCode.ClassLib.csproj

cd .\src\CSharpWithVSCode.ConsoleApp\
dotnet add reference ..\CSharpWithVSCode.ClassLib\CSharpWithVSCode.ClassLib.csproj