What I should return from WebAPI ?

 

There are several approaches when returning code from WebAPI .  Let’s frame the problem: say we have a Person controller with 2 actions:

– a GET {id}  – that retrieves the Person with id

– a POST {Peron}  – that tries to verify the validity of the Person and then saves to database.

We will answer to some questions:

1.What we will return if the person with id does not exists ?

2. What happens with the validation about the Person  ?
Let’s see the Person class.

public class Person: IValidatableObject
{
    public int ID { get; set; }
    public string  Name { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        yield return new ValidationResult("not valid not matter what");
    }
}

 

First approach: Do nothing

What I mean is just return the Person , even if it is null.

1.1. The GET

[HttpGet("{id}")]
public Person GetPerson(int id)
{
var p = RetrieveFromDatabase(id);
return p;
}

The problem is that when we return null from an action, there are no response data from the HTTP call-  and the javascript should handle it .

 

1.2 The POST – no problem . [ApiController] should handle the validation and return BadRequest if not validate

 

Second approach:  Return standard HttpCodes

2.1 The GET


[HttpGet("{id}")]
public ActionResult<Person> GetPerson404(int id)
{
    var p = RetrieveFromDatabase(id);
    if (p == null)
        return NotFound($"{nameof(Person)} with {id} are not found");

    return p;

}

We intercept the null and return standard 404 HttpCode . In that case, I strongly suggest to add a message to the end-caller – to know that the reason is not that the http call was a problem, but the Person was not found

2.2 The POST – no problem . [ApiController] should handle the validation and return BadRequest if not validate

 

Third approach: Return OK with a custom ReplyData class

The ReplyData can look this way

public class ReplyData<T>
{
    public bool Success { get; set; }
    public string Message { get; set; }
    public T ReturnObject { get; set; }
}

2.1 The GET

This action is over simplified – the code just returns the ReplyData from the database.

[HttpGet("{id}")]
public ReplyData<Person> GetWithReply(int id) {

    return RetrieveWithReplyFromDatabase(id);
}

private ReplyData<Person> RetrieveWithReplyFromDatabase(int id)
{
    try
    {
        Person p = null;//retrieve somehow
        if (p == null)
        {
            var r = new ReplyData<Person>();
            r.Success = false;
            r.Message = "Cannot find person with id " + id;
            return r;
        }
        else
        {
            var r = new ReplyData<Person>();
            r.Success = true;
            r.ReturnObject = p;

            return r;
        }
    }
    catch(Exception ex)
    {
        var r = new ReplyData<Person>();
        r.Success = false;
        r.Message = ex.Message;
        return r;
    }
}

2.2 The POST

This is somehow complicated – the [ApiController] , if not valid, return a 400 BadRequest . So we should modify this with a custom middleware to return the same ReplyData

public class From400ValidationToReply : IMiddleware
{
public async Task InvokeAsync(HttpContext context, RequestDelegate next)
{
    try
    {
        var originalStream = context.Response.Body;
        var bufferStream = new MemoryStream();
        context.Response.Body = bufferStream;
        await next(context);
        bufferStream.Seek(0, SeekOrigin.Begin);
        if (context.Response.StatusCode != 400)
        {
            await bufferStream.CopyToAsync(originalStream);
            return;
        }
        var reader = new StreamReader(bufferStream);
        var response = await reader.ReadToEndAsync();
        if (!response.Contains("errors"))
        {
            await bufferStream.CopyToAsync(originalStream);
            return;
        }

        context.Response.StatusCode = 200;

        var r = new ReplyData<Person>();
        r.Success = false;
        r.Message=response;
        var text = JsonSerializer.Serialize(r);
        var bit = Encoding.UTF8.GetBytes(text);
        context.Response.ContentLength = bit.Length;
        await originalStream.WriteAsync(bit);

    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
        throw;
    }
}

And the problem is that will affect all the request pipeline….

Conclusion:
I would choose 2 . But … your choice… ( and , for an advanced discussion, please read https://blog.ploeh.dk/2013/05/01/rest-lesson-learned-avoid-hackable-urls/ )

Automate the generation of the e-book

What I have found important in composing the e-book with examples was automating the work of generating the e-book. I have had a json file ( 10 years ago I have used xml ) and some specific folders with the chapters content. I have had also a template for each example chapter – that was ensuring all chapters look the same.

As an example , you can look  at https://github.com/ignatandrei/RSCG_Examples/tree/main/ApplicationVersion  and at  https://github.com/ignatandrei/RSCG_Examples/tree/main/CopyConstructor

This is generated automatically with

var m = new MultiGenerator(folder);
             await m.GeneratePost();
             await m.GenerateReadMeForEach();
             await m.GenerateFrontReadMe();
             await m.GenerateForImages(Path.Combine(folder, “docs”, “images”));
             await m.GenerateForEmail();
         }

Also, pandoc ( see previous post ) it will generate the book from markdown.

Code as picture and PowerAutomateDesktop

I want to make an e-book from RCSG . For this I need to put the code into the book in a nice form. However , the Word document and the PDF and the HTML all have the ideas of formatting the code. How one can accommodate various formats ? Short answer: picture. What if I take a screenshot of the code , as it is formatted in VS / VS Code ? 

But how ? One idea is to open VS and take screenshot  = but it is too resource intensive.

Other idea is internet- I found 2 sites: https://ray.so/  and https://carbon.now.sh/  . What if I use those sites  ?

The obvious solution is Selenium . The other is iMacros . I was thinking to another solution – Power Automate Desktop . Even in preview, it can record the browser actions ( open, goto url, click buttons) and even execute javascript :

function ExecuteScript() {
document.getElementsByClassName(‘jsx-2004545632 ‘)[0].click();
document.getElementById(‘export-clipboard’).focus();
document.getElementById(‘export-clipboard’).click();

  }

 

So I have made a flow to execute https://carbon.now.sh/   and another to save the image in paint ( and crop )

You can find the end result here : https://ignatandrei.github.io/RSCG_Examples/#rscg-number-1—thisassembly

Making a book from (examples) markdown

I want to make a book from my RSCG examples  https://github.com/ignatandrei/RSCG_Examples . The easy way is to transform the .md files into separate chapters.

I have tried initially node with  markdown-pdf and  pdf-merger-js , but I have been going then full speed with pandoc . To generate both Word and Index.md I have used this:

pandoc.exe -d pandocHTML.yaml -o ../docs/index.md -t gfm

pandoc.exe -d pandocHTML.yaml -o ../docs/index.docx

The pandocHTML.yaml is here:

from: gfm

# reader: may be used instead of from:

# to: docx

# output-file:  index.docx

# to: gfm

# output-file:  ../docs/index.md

# writer: may be used instead of to:

# leave blank for output to stdout:

reference-doc: customWord.docx

# leave blank for input from stdin, use [] for no input:

input-files:

– ../book/about.md

– ../book/whatIs.md

– ../ApplicationVersion/README.md

– ../Enum/README.md

– ../JsonToClass/README.md

– ../CopyConstructor/README.md

– ../DTOMapper/readme.md

– ../SkinnyControllers/README.md

– ../DP_Builder/readme.md

– ../MetadataFromObject/README.md

– ../DynamicMocking/readme.md

– ../MethodDecorator/README.md

– ../PartiallyFunction/readme.md

– ../IFormattable/readme.md

– ../DP_Decorator/README.md

– ../PropertyExpressionGenerator/readme.md

– ../book/others.md

– ../book/conclusion.md

# or you may use input-file: with a single value

# defaults:

# – customWord.docx

standalone: true

self-contained: true

# metadata values specified here are parsed as literal

# string text, not markdown:

metadata:

title: RSCG Examples

author:

  – Andrei Ignat

# Note that these take files, not their contents:

include-before-body: []

include-after-body: []

include-in-header: []

resource-path: [“.”]

# ERROR, WARNING, or INFO

verbosity: INFO

log-file: log.json

table-of-contents: true

toc-depth: 3

# number-sections: true

# a list of offsets at each heading level

number-offset: [0,0,0,0,0,0]

# toc: may also be used instead of table-of-contents:

shift-heading-level-by: 1

section-divs: true

identifier-prefix: foo

title-prefix: “”

strip-empty-paragraphs: true

# lf, crlf, or native

eol: lf

strip-comments: false

indented-code-classes: []

ascii: true

default-image-extension: “.jpg”

fail-if-warnings: false

dump-args: false

ignore-args: false

trace: false

As you see , I have put the .md files to be processed. Another thing that I have the need is to have a custom word template – to put page breaks after Heading 2. You can download from https://github.com/ignatandrei/RSCG_Examples/blob/main/print/customWord.docx

Andrei Ignat weekly software news(mostly .NET)

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