TValue GetOrAdd(TKey key, Func<TKey, TValue> valueFactory);

var dictionary = new ConcurrentDictionary<string, string>();
 
var value = dictionary.GetOrAdd("key1", x => "item 1");
Console.WriteLine(value);
 
value = dictionary.GetOrAdd("key1", x => "item 2");
Console.WriteLine(value);

item 1
item 1

using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;

namespace Sample
{
    class Program
    {
        static void Main(string[] args)
        {
            var dictionary = new ConcurrentDictionary<int, int>();
            var options = new ParallelOptions { MaxDegreeOfParallelism = 100 };
            var addStack = new ConcurrentStack<int>();

            Parallel.For(1, 1000, options, i =>
            {
                var key = i % 10;
                dictionary.GetOrAdd(key, k =>
                {
                    addStack.Push(k);
                    return i;
                });
            });

            Console.WriteLine($"dictionary.Count: {dictionary.Count}");
            Console.WriteLine($"addStack.Count: {addStack.Count}");
        }
    }
}

dictionary.Count: 10
addStack.Count: 13

namespace Sample
{
    class Program
    {
        static void Main(string[] args)
        {
            var dictionary = new ConcurrentDictionary<int, Lazy<int>>();
            var options = new ParallelOptions { MaxDegreeOfParallelism = 100 };
            var addStack = new ConcurrentStack<int>();

            Parallel.For(1, 1000, options, i =>
            {
                var key = i % 10;
                dictionary.GetOrAdd(key, k => new Lazy<int>(() =>
                {
                    addStack.Push(k);
                    return i;
                }));
            });

            // Access the dictionary values to create lazy values.
            foreach (var pair in dictionary)
                Console.WriteLine(pair.Value.Value);

            Console.WriteLine($"dictionary.Count: {dictionary.Count}");
            Console.WriteLine($"addStack.Count: {addStack.Count}");
        }
    }
}

10
1
2
3
4
5
6
7
8
9
dictionary.Count: 10
addStack.Count: 10

    public class LazyConcurrentDictionary<TKey, TValue>
    {
        private readonly ConcurrentDictionary<TKey, Lazy<TValue>> _concurrentDictionary;
        public LazyConcurrentDictionary()
        {
            _concurrentDictionary = new ConcurrentDictionary<TKey, Lazy<TValue>>();
        }

        public TValue GetOrAdd(TKey key, Func<TKey, TValue> valueFactory)
        {
            var lazyResult = _concurrentDictionary.GetOrAdd(key,
             k => new Lazy<TValue>(() => valueFactory(k), LazyThreadSafetyMode.ExecutionAndPublication));
            return lazyResult.Value;
        }
    }

A Microsoft exec has warned that Internet Explorer is a ‘compatibility solution’ and should only be used selectively. Preaching to the choir here, and this is, we suspect, the very end of IE's long story for us.

declare @t table
(id char(1) primary key,
parent char(1));

insert @t values 
('A',null),                                   --Level 1
('B', 'A'), ('C', 'A'),                       --Level 2
('D', 'B'), ('E', 'B'),('R','B'), ('F', 'C'), --Level 3
('G', 'D'),  --Level 4
('H', 'G'), ('I', 'G');                       --Level 5

;with cte as
(
select id, rnk=0 from @t
where parent = 'A'
 
union all
 
select t.id, rnk+1
from cte join @t t
on cte.id = t.parent
)
select *
  from cte
 where not exists
       (select *
          from @t
         where parent = cte.id);

;with cte as
(
select id, rnk=0 from @t
where parent = 'A'

union all

select t.id, rnk+1
from cte join @t t
on cte.id = t.parent
)
select *
from
(
   select *, dense_rank() over(order by rnk desc) rk
     from cte
)t
where rk = 1

Vertical Slice Architecture, not Layers! 

Why Vertical Slice Architecture? Nobody wants to deal with a system that is hard to change and easy to introduce bugs because it's a spaghetti code mess of various technical concerns. Clean Architecture is popular because it separates concerns into many different layers. But why are we organizing code by layers? Does adding a new feature require you to modify files across multiple projects in your UI, business, and data access layers? Vertical Slice Architecture is about how you organize code and focus on features instead of technical layers will make your system easier to change. 

TL;DR: .NET 7 is fast. Really fast. A thousand performance-impacting PRs went into runtime and core libraries this release, never mind all the improvements in ASP.NET Core and Windows Forms and Entity Framework and beyond. It’s the fastest .NET ever. If your manager asks you why your project should upgrade to .NET 7, you can say “in addition to all the new functionality in the release, .NET 7 is super fast.” 

We are excited to announce the release of .NET Core 1.0, ASP.NET Core 1.0 and Entity Framework 1.0, available on Windows, OS X and Linux! .NET Core is a cross-platform, open source, and modular .NET platform for creating modern web apps, microservices, libraries and console applications.

This release includes the .NET Core runtime, libraries and tools and the ASP.NET Core libraries. We are also releasing Visual Studio and Visual Studio Code extensions that enable you to create .NET Core projects. You can get started at https://dot.net/core. Read the release notes for detailed release information. 

• Solution Explorer: touch pad gesture scroll is too sensitive.
• C++/CLI: std::move causes std::unique_ptr parameter to be destructed before function call.
• live share shows "failed to sign in" .
• VS symbol search fails to find symbols.
• Undo randomly stops working.
• VS "Go to defintion" functionality frequently does not work.
• Linux CMake Intellisense HeaderCache not downloading headers for 15.8.0 Preview 4.0.
• When opening a project that requires elevated permissions, Visual Studio does not automatically open the selected project after restarting elevated.
• vcpkgsrv.exe crashes.
• New Visual Studio Code keymap not applying?. 

• TLS 1.0: The request was aborted: Could not create SSL/TLS secure channel.
• Task List with filter set to Entire Solution doesnt display tasks/todos when the file is closed.
• Fatal error C1001: An internal error has occurred in the compiler.
• VS 2019 Preview 1 - EF6 edmx file cannot be saved.
• vcruntime140.dll should be made available on Microsoft Symbol Server.
• Static Analyser, Custom Rule Set (C++) does not execute included default sets.
• VS2019 Preview: Azure Function publishing does not work.
• References window does not remember its position.
• Missing formatting option for pointers and references.
• Microsoft.TeamFoundation.Client, Version=15.0.0.0 assembly not found when create a new web project. 

What is the keynote about?
How do we write modern C++ code?
Guideline support library and Static analysis
Call to action for the C++ community!
Enhancing productivity by eliminating whole classes of bugs
Extending the C++ core guidelines
What do you expect from these static analysis checkers?
How can I get started?