DEV Community: Jozef Chmelar

Microsoft.NET.Sdk.Common.targets was not found

Jozef Chmelar — Thu, 30 Sep 2021 07:54:41 +0000

After update of Visual Studio and .NET I got an error that seems to repeat pretty often. Unfortunately I forget how to deal with it every single time.

The issue looks like this

msbuild //works
dotnet build

Results in following error

C:\Program Files\dotnet\sdk\5.0.41\Current\SolutionFile\ImportAfter\Microsoft .NET.Sdk.Solution.targets(14,3): error MSB4619: The imported
project "C:\Program Files\dotnet\sdk\5.6.100\Sdks\Microsoft .NET.Sdk\targets\Microsoft.NET.Sdk.Common.targets" was not found. Confirm that
the expression in the Import declaration "C:\Program Files\dotnet\sdk\5.0.41\Sdks\Microsoft.NET.Sdk\targets\Microsoft .NET.Sdk.Common.targets" is correct, and that the file exists on disk.

Build FAILED.

C:\Program Files\dotnet\sdk\5.0.41\Current\SolutionFile\ImportAfter\Microsoft .NET.Sdk.Solution.targets(14,3): error MSB4619: The imported
project "C:\Program Files\dotnet\sdk\5.6.100\Sdks\Microsoft .NET.Sdk\targets\Microsoft.NET.Sdk.Common.targets" was not found. Confirm that
the expression in the Import declaration "C:\Program Files\dotnet\sdk\5.0.41\Sdks\Microsoft.NET.Sdk\targets\Microsoft .NET.Sdk.Common.targets" is correct, and that the file exists on disk.

When you try to print the file Microsoft.NET.Sdk.Solution.targets

cat "C:\Program Files\dotnet\sdk\5.0.401\Current\SolutionFile\ImportAfter\Microsoft.NET.Sdk.Solution.targets"

Notice this line

  <Import Project="$(MSBuildSDKsPath)\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.Common.targets" />

The MSBuildSDKsPath variable is important here. It looks like it's looking at the wrong folder.

When I created an enviroment variable with the name MSBuildSDKsPath and value C:\Program Files\dotnet\sdk\5.0.401\Sdks it works!

Don't forget to restart your terminal.

Covariance and contravariance by example.

Jozef Chmelar — Sat, 23 Jan 2021 12:42:12 +0000

Covariance and contravariance are very spooky words.

I use these words if I want to sound very smart - and it usually works. No one really knows what the hell it is.

As I want to explain this topic as simple as possible (but not simpler) I'll try to avoid these smart-sounding words.

I'm going to implement a Repository pattern with the use of generics to explain this topic.

I'll use C# for my examples, it's pretty similar in languages like Java or Kotlin.

You already know half of it!

Let's define a few simple classes.

record Person(string Name);
record Employee(string Name) : Person(Name);
record RemoteEmployee(string Name, string location) : Employee(Name);

Create a few employees and put them inside a collection.

IEnumerable<Employee> people = new List<Employee>
{
    new Employee("Andrew"),
    new RemoteEmployee("Karen","USA")
};

Since an Employee is also a Person I should be able to do this.

IEnumerable<Person> people = new List<Employee> // It's not <Employee> anymore.
{
    new Employee("Andrew"),
    new RemoteEmployee("Karen","USA")
};

So if an Employee is also a Person I can use a more generic type on the left side of the assignment. AKA Covariance!

Simple right?

Since I mentioned a generic type let's make something where we can make use of generics. Let's save the data in a database.

| Fun fact : Generics were introduced in C# 2.0, released in 2005, along with Visual Studio 200.

Should I use MySQL, Excel, SQL Server, SQLite or Postgres? The answer is - we shouldn't have to care. All I want to do is insert some data and get it back later. Here a repository pattern comes to rescue!

interface IRepository<T>     // "T" stands for "data of some type"
{
    void Insert(T item);     // I want to insert some data.
    T Get(string id);        // and get it 
    IEnumerable<T> GetAll(); //            back later
}

I implemented a very simple repository which stores the object in a Json file on a disk. You can see it here.

When you implement a repository like this you encounter a problem while implementing the Insert method.
How to insert the data in such a way that I can retrieve it later?
There's an id in the Get method but under what id would you Insert the data?

You have multiple options here
1. Let a database handle it - The database could generate some Guid (like Mongo) or a relational database could generate a primary key.
2. Use a hash code or a ToString of an object - But you may never get the object back, so never do that.
3. Enforce an Id before it is added to a database.
4. Some other idea.

You're in charge, not a database or a hash function so I'm going with the option #3.

I want all my persistent objects to implement an IEntity interface.

interface IEntity { string Id { get; } }

record Person(string Name) : IEntity { public string Id => Name; } // Name is not the best Id of course.

I also have to enforce the rule on the interface itself.

interface IRepository<T> where T : IEntity  // "T" stands for "data of some type" where the data also has an Id.

Now I can store my list of employees in a database!

static void Main(string[] args)
{
    var employeesRepository = new FileRepository<Employee>();
    AddEmployees(employeesRepository);  // Add a list of employees to a repository
    ReadAndPrintRepository(employeesRepository);     // Read the repository and print users.
}

static void AddEmployees(IRepository<Employee> repository) 
    => new List<Employee>
        {
            new RemoteEmployee("Karen","Usa"),
            new Employee("Karen")
        }.ForEach(repository.Insert);

static void ReadAndPrintRepository(IRepository<Employee> repository) 
    => repository
        .GetAll()
        .ToList()
        .ForEach(Console.WriteLine);

This all works, which is great. But an Employee is also a Person so I'd like to change make a small change.

static void ReadAndPrintRepository(IRepository<Person> repository)

Suddenly you get an error

cannot convert from 'FileRepository<Employee>' to 'IRepository<Person>'csharp(CS1503)

But why? It works on the example above!

To quote me "So if an Employee is also a Person I can use a more abstract type on the left side of the assignment. AKA Covariance!

What's the difference? Well if you take a look on the IEnumerable (or Collection in Java) interface it's defined like this.

public interface IEnumerable<out T> : System.Collections.IEnumerable

The out keyword is crucial here. It says to the compiler - use the type T or a more abstract/derived type. The type T is a covariant parameter. It allows some change, a variance.

But why the out keyword? Why not in or covariant or leave me alone and work plz?

Let's add an out keyword to our interface and let's see.

Invalid variance: The type parameter 'T' must be contravariantly valid on 'IRepository<T>.Insert(T)'. 'T' is covariant. csharp(CS1961)

(╯°□°）╯︵ ┻━┻

Whaaat?

Well. When you specify the out keyword it means that the interface can only OUTPUT the type T. It cannot take an input of type T, like it does in the Insert method.

I'll remove the Insert method from the IRepository interface and move it to IWriteOnlyRepository. To have some symmetry in the codebase I'll introduce an IReadOnlyRepository and merge them in the IRepository.

interface IWriteOnlyRepository<T>
{
    void Insert(T item);
}

interface IReadOnlyRepository<out T>
{
    T Get(string id);
    IEnumerable<T> GetAll();
}

interface IRepository<T> : IWriteOnlyRepository<T>, IReadOnlyRepository<T> where T : Entity
{
}

Now when you use the IReadOnlyRepository interface as a parameter in the ReadAndPrintRepository method you won't get an error anymore!

┬─┬ノ( º _ ºノ)

static void Main(string[] args)
{
    var employeesRepository = new FileRepository<Employee>();
    AddEmployees(employeesRepository);
    ReadAndPrintRepository(employeesRepository);
}

static void ReadAndPrintRepository(IReadOnlyRepository<Person> repository) => repository.GetAll().ToList().ForEach(Console.WriteLine);

static void AddEmployees(IRepository<Employee> repository) => new List<Employee>
    {
        new Employee("Bjork"),
        new RemoteEmployee("Karen","Usa")
    }.ForEach(repository.Insert);

Everything works as expected. Life's good. But what if I add a special method which will only handle RemoteEmployees?

static void AddRemoteEmployees(IRepository<RemoteEmployee> repository)
    {
        //some operations only valid for RemoteEmployee
        //OnlyRemoteEmployeeMethod(remoteEmployee)
        repository.Insert(new RemoteEmployee("Andrew","Canada"));
        repository.Insert(new RemoteEmployee("Carol","UK"));
    }

Unfortunately you'll get this error
cannot convert from 'FileRepository<Employee>' to 'IRepository<RemoteEmployee>'.

The FileRepository implements the interface IRepository<Employee> so only an Employee can be added into the repository. You can say that is very rigid. It won't allow any variance, therefore it is Invariant.

The IWriteOnlyRepository has currently the same problem as IRepository it does not allow any variance. Since we have an out modifier on the IReadOnlyRepository, don't we have an in modifier we can use?

Yes, we do! When you specify the in keyword it means that the interface can only accept an INPUT of the type T. Since we are only using the type T as an input and we never return in we can mark the input type as contravariant using the in keyword.

interface IWriteOnlyRepository<in T>
{
    void Insert(T item);
}

The last thing to do is to change the interface in the method. Since IRepository doesn't allow any variance, we have to use a more flexible interface which is the IWriteOnlyRepository. RemoteEmployee is more specific than Employee, but since our IWriteOnlyRepository is marked with an in keyword it doesn't mind more specific types. AKA contravariance.

static void AddRemoteEmployees(IWriteOnlyRepository<RemoteEmployee> repository) => new List<RemoteEmployee>
    {
        new RemoteEmployee("Andrew","Canada"),
        new RemoteEmployee("Carol","UK")
    }.ForEach(repository.Insert);

It works!
(☞ﾟヮﾟ)☞

GitHub repo with full code = link

Summary

When your interface allows you to use a single type, it offers no flexibility, no variance, therefore it's invariant.

You can go through a list of employees and treat them as Person`s, because they have a common trait - covariance

You can't treat the list of employees as a list of managers, but you should be able to add a manager to a list of employees. This way you're approaching the problem from the opposite (contra) side - contravariance

I hope I made this weird topic a bit more clear!

Strong named assemblies — To sign or not to sign?

Jozef Chmelar — Mon, 28 Dec 2020 20:16:00 +0000

Should you sign your .NET assemblies or not? That is the question.

According to the Betteridge’s law of headlines the answer should be no. Unfortunately you’re going to have to decide for yourself.

I gathered some info and made a decision accordingly. Time has passed and I do not regret my decision.

Here’s the data:

Do not rely on strong names for security. They provide a unique identity only.
You can use different versions of the same assembly.
Tampering with strongly signed assembly is possible. Since .NET 3.5 can be bypassed, because it was slow. [link]
Strong naming is probably causing the issue we had with app.config [link]
Strong named assembly can only reference other strong named assemblies [link]
Vladimir Khorikov doesn't sign his libs, since no one is doing it anymore [link]
According to Microsoft, you should strong sign your dlls [link]
This thing exists: strong namer – sign dlls which are not signed [link]
NewtonSoft.Json, Serilog, TwinCAT.Ads - signed
Interesting blog postshttps://jbp.dev/blog/signing-net.html
This guy changed his mind
- March 2016 Still Strong-Naming your Assemblies? You do know 's 2016, right?
- September 2018 Start Strong-Naming your Assemblies!
To those still skeptical of strong-naming their assemblies, I propose a compromise solution: do strong-name your assemblies, but only increment the assembly version for major releases! Json.NET has been using this approach to avoid binding redirects since 2014, and as far as I can tell, with relative success!
This git diff https://github.com/dotnet/corefx/pull/33784/files#

Conclusion

Microsoft recommends to sign assemblies; critical libraries are signed as well. We want to ensure that specific versions will always work with each other. We should also able to sign dlls which are not signed by default. Therefore, I recommend to use strong naming.

Simple tip for your product meetings.

Jozef Chmelar — Mon, 12 Oct 2020 17:22:39 +0000

I'm busy

Print "KEEP IT LEAN" on a piece of paper and put the paper on a visible place during your meeting.

Like this

I have a minute

Marketing, SEO, BizDev, Product owner and WebDev people.

We spent two days locked up in a meeting room with a simple goal.

Design a website which would enable our clients to buy and manage their licenses.

2 days is way too long.

I was so upset, angry and tired after the first day. It felt like we have done a big amount of nothing.

Next morning, I printed out "KEEP IT LEAN" on a piece of paper with the biggest font that fit. Here I prepared it for you

Now when we heard a feature like:

"Merge private accounts with company accounts so they can (whatever was the argument)"

Someone would just grab that piece of paper and remind everyone that that's not the problem we're solving.

We were done by lunch-time.

Soft skills - communication tips

Jozef Chmelar — Wed, 27 Nov 2019 20:42:25 +0000

unsplash.com/@akson

Your next promotion

What do you think will land you your next promotion? Next framework you're going to learn? Haskell programming? Great architecture on that app you developed?

Yeah. Maybe.

You might be the best programmer around your office. However, in real world you don't have to be THE BEST to be promoted. If you can't talk to a client or no one in the office wants to talk to you, do you think you'll be promoted?

Yeah. No.

Introduce yourself with a memorable association

I’m Jozef and I like wakeboarding🏄‍♀️!

Jacob 😊
Emma👩
Lucas 🧑🏿
Sarah👧🏼

They have one thing in common. You already forgot their names…and they forgot yours.

People forget names way too often. My name is the sweetest, best sounding song in the world. And I love it! And you love yours. It’s the sound you hear even when no one said it…

What was the name of that guy with wake-board 🤔? Jozef !

Make it easy to remember your name :) It makes it easier to talk to you.

You are worthy

unsplash.com/@andrewtneel

Once you put someone on a pedestal there’s only way they can look at you. You’ll always be bellow them. Don’t allow this to happen. Your time has value, you have value.

I'm sorry for the code I wrote → Yay! Good that you noticed.
I’m sorry that I’m late → Thank you for waiting for me
I’m sorry about the delay → Thanks for your patience

Constant apologizing may appear as you are not confident enough to appreciate yourself.

Next time you’re going to have job interview, you can refer to it as a meeting about future cooperation. Remember that the company wants you and you want to work there.

Wallet is a very sensitive part of the body

unsplash.com/@andrea_natali

I found myself in a situation when I was the "sales guy" even though I'm a developer. It might happen to you! In this case, these are my notes.
I would like to offer you a presentation of our latest product…Might be the most NO-NO sentence in the universe.

Product
Sale
Presentation
Offer

Especially these words make me feel like you want to get into my wallet. I don’t like that. Don’t make it so obvious, silly.

I could show you the result of our work, I believe it may be beneficial for you. — Sounds a bit better, doesn’t it?

But, why?

unsplash.com/@jannerboy62

I want to give you a raise, but bla bla bla bla…
Your job performance is great, but blah blah bla blah…

This translates into :

I don’t want give you a raise.
Your job performance sucks.

Notice the “.” at the end of translated sentences. They end right there. Whatever follows “but” is just irrelevant. You already know this, but…

I recommend to avoid this word. Nonetheless there’s use for it, when you turn your sentence around.

Why

Why did you put this code…
Why is it written like this…

Starting a sentence with why feels very accusingly or threatening. Just use different words

What’s the reason for …
What was the thinking behind this …

Be positive

unsplash.com/@adamjang

Next time you’re going to write an email try to sound friendly, positive. It’s very important to be perceived as a positive person — not a trouble maker.

It’s not easy to be positive. You have to change your thinking a bit.

I have to go for a run.
I have to go to the gym.
I have to go to school.

They all sound very bad on their own. But once you attach a goal or something bigger to your activity…it’s not that bad 😊

I want to be thin and healthy so I’m going for a run!
I want to have that beach body so I have to lift some weights!
I want to be educated and well perceived in the future so I want to study Remember that you and the person on the other side of the line, may have more in common than you think :).

Conclusion

unsplash.com/@alex_tsl

You may have heard a lot of tips like this. It’s easy to forget about them unless you apply them in your everyday life.

Communication is something you will train for the rest of your life. Just pick a few from this tips…one at a time and you’ll be amazed by the results.

Your customers will prefer you before that trouble maker. You will be the problem solver.

How I built a simple compiler — Markdown to HTML

Jozef Chmelar — Fri, 22 Nov 2019 12:12:41 +0000

A colleague of mine, who happens to be my ̶ b̶o̶s̶s̶ leader wrote a really cool compiler. It’s not a cool CRUD app or complicated animation.

IT’S A COMPILER. Used in the production environment. And it’s not backed up by a community or a big company.

I think that’s pretty cool…I would like to code cool stuff...So I decided I’m going to write a compiler!

So I did…because I could do following

Learn more about the magic of compilers
Learn something else than a new JavaScript framework
Achieve one of my goals.
Code something different.
Understand the codebase more in-depth

How?

Foundation of my compiler is built on top of Irony. It’s a .NET Language Implementation Kit. Unfortunately, there’s not a lot of info or tutorials online. Even with the little amount of online documentation, I was able to define language grammar, so I can parse the input.

I’m using Irony’s NonTerminal and Terminal classes to define my markdown.

Grammar

Now it’s time to define Grammar rules. Grammar is defined using Backus-Naur form. Irony overloads C# operators and makes it really easy to define grammar.

It’s so easy to read. Let’s dive in.

Bold text has to start with a star * followed by a Text ending with a star *. Text can be StyledText or PlainText. But StyledText can Bold, Italics or U͟n͟d͟e͟r͟s͟c͟o͟r͟e͟. Do you see the little hack? Now Bold text can also be underscore and italics! Same thing with Header. Underscore header? No problem, since it fits our grammar rules.

It's not THAT complicated

If you notice the definition of NonTerminals and Terminals you will see the second parameter is a type of Ast node. This way I could map my parse tree to AST. It was really a pain to achieve this. I searched StackOverflow, second page of google results…no luck. My solution might not be the best in the world but it works. It’s a function which creates an instance of the type you provide it with.

It’s much easier to work with AST than parse tree :) That’s why you do it.

Parse vs AST tree

From Abstract Syntax Tree to HTML

Grammar is defined, AST looks good. Now I had to do a thing which I’ve been successfully avoiding for like 5 years. I had to learn the visitor pattern. It makes much more sense now, than in a university few years ago.

Accurate description of visitor pattern

This is how Irony accepts Visitor when traversing the tree.

And this is how I wrote my HTML visitor. Before you visit a node write you tag, after that he will visit every child.

When you encounter PlainTextAst, output the text we parsed

And now just visit the root

Voilà!

From this

#"H1 Heading"
#_"H1 undescore heading"_
##"H2 Heading"
*"This is bold text"* "and this is regular text"
"Following three items should be in a list, this is plaintext"
- "Plaintext list item"
- *"Bold List item"*
- _*"Underscore bold list item"*_
- _"Underscore  list item"_
#"This is heading again"

To this

<div>
  <h1>H1 Heading</h1>
  <h1>
    <u>H1 undescore heading</u>
  </h1>
  <h2>H2 Heading</h2>
  <b>This is bold text</b>
  <p>and this is regular text</p>
  <p>Following three items should be in a list, this is plaintext</p>
  <ul>
    <li>Plaintext list item</li>
    <li>
      <b>Bold List item</b>
    </li>
    <li>
      <u>
        <b>Underscore bold list item</b>
      </u>
    </li>
    <li>
      <u>Underscore  list item</u>
    </li>
  </ul>
  <h1>This is heading again</h1>
</div>

It works!

Conclusion

I wanted to write a compiler from my markdown to HTML. I picked up great available tools to achieve it and did it. You don’t have to start in assembly to write your own parser, compiler, language, operating system…

Try it. Do it. Solve it.

DEV Community: Jozef Chmelar

Microsoft.NET.Sdk.Common.targets was not found

Covariance and contravariance by example.

You already know half of it!

Summary

Strong named assemblies — To sign or not to sign?

Conclusion

Simple tip for your product meetings.

I'm busy

I have a minute

Soft skills - communication tips

Your next promotion

Introduce yourself with a memorable association

You are worthy

Wallet is a very sensitive part of the body

But, why?

Why

Be positive

Conclusion

How I built a simple compiler — Markdown to HTML

How?

Grammar

From Abstract Syntax Tree to HTML

Voilà!

It works!

Conclusion

jozefchmelar / MarkdownCompiler

My tiny compiler :) https://jozefchmelar.com/MarkdownCompiler/