Most of my large projects are using Entity Framework. And Entity Framework is known to sometimes create crazy sql requests. Or rather it easily allows developers to create crazy queries. It is really easy to throw couple .Include() into your query and then return objects as they come from EF:

var products = dbContext.Products.Include(p => p.Tags)
                                 .Include(p => p.Reviews)
                                 .ToList(); // first query
foreach(var prod in products)
{
    var reviewers = prod.Reviews.Select(r => r.Owner).ToList(); // N+1
}

The above code is fictional, but most likely will produce N+1 issue. N+1 issue is when you don’t just issue a SELECT query, but follow up every returned row by another SELECT query to retrieve related entries. This is caused by EF feature called Lazy Loading. Read better explanation about Lazy Loading problem here. Basically think that your first query for Products returns 1000 records. Then in case of N+1, operation inside of foreach loop will produce another thousand queries to your database.

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UPD There is a part 2 of this blog-post explaining how to do roles and fixing a minor issue with authentication.

UPD If you are on Windows 10 and get “System.IO.FileNotFoundException: The system cannot find the file specified”, have a look on this page. Thanks to David Engel for this link.

A while back I had to implement a login system that relied on in-house Active Directory. I did spend some time on figuring out how to work this in the nicest possible ways.

One of the approaches I used in the past is to slam Windows Authentication on top of the entire site and be done with it. But this is not very user-friendly – before showing anything, you are slammed with a nasty prompt for username/password. And you need to remember to include your domain name in some cases. I totally did not want that on a new green-field project. So here goes the instructions on how to do a nice authentication against your Windows Users or in-house hosted Active Directory.

For this project I’ll use Visual Studio 2015. But steps for VS2013 will be the same. Can’t say anything nice about any earlier versions of Visual Studio – I don’t use them anymore.

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This post will be a dumping ground of links, problems and solutions related to Swagger. I’ll be putting updates here as I go along


I’m starting a new project and we would love trying new things. This time we would like to jump on the whole Azure Api Applications with Swagger as a descriptor of API.

Great article “What is Swagger”

Here is the whole Swagger Spec – have a look what is possible.

Here is the pretty cool page with Swagger file editor

Tutorials for ASP.Net

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I have seen a fair amount of questions on Stackoverflow asking how to prevent users sharing their password. Previously with MembershipProvider framework it was not a simple task. People went into all sorts of crazy procedures. One of the most common was to have a static global list of logged-in users. And if a user already in that list, the system denied their second login. This worked to an extent, until you clean cookies in the browser and try to re-login.

Luckily now Asp.Net Identity framework provides a simple and clean way of preventing users sharing their details or logging-in twice from different computers.

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I’m an avid user on StackOverflow in questions about Asp.Net Identity and I attempt to answer most of the interesting questions. And the same question comes up quite often: users try to confirm their email via a confiramtion link or reset their password via reset link and in both cases get “Invalid Token” error.

There are a few possible solutions to this problem.

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The title is quite vague, but this is the best I can call this post. Bear with me, I’ll explain what I mean.

While working with Asp.Net MVC, in Razor views I use Html helpers a lot. My view end up looking like this:

@Html.TextBoxFor(m => m.Title)
@Html.TextAreaFor(m => m.Description)

And later if I write JavaScript and need to reference one of the input fields, I usually do this:

var title = document.getElementById("Title");
var description = document.getElementById("Description");

or if you use jQuery you go like this:

var title = $("#Title");
var description = $("#Description");

This is fine and works. Until you start renaming field names in your model. And then you need to track down where you hard-coded the input id. And many times these references slip away (they do from me!) and remain unchanged.

Would it not be great if these changed could be picked up automatically? or even better, do some sort of strongly-typed reference to the element if it is used in JavaScript?

Just use @Html.IdFor(m => m.Name)

And your JS code would look like this:

var title = document.getElementById("@Html.IdFor(m => m.Title)");
var description = $("#@Html.IdFor(m => m.Description)");

Below I’ve re-invented the wheel. [Facepalm]

So I trolled through MVC source code and figured out how it generates id’s for elements and here are my findings:

using System;
using System.Linq.Expressions;
using System.Web.Mvc;

public static class HtmlHelpers
{
    public static String ElementId<T, TResult>(this HtmlHelper<T> htmlHelper, Expression<Func<T, TResult>> selector)
    {
        var text = System.Web.Mvc.ExpressionHelper.GetExpressionText(selector);
        var fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(text);
        var id = TagBuilder.CreateSanitizedId(fullName);

        return id;
    }
}

As you can see, I have not made any custom code, all components are from MVC and are applied in the same order as MVC does when it generates id for elements when you call for @Html.EditorFor(). So this guarantees the provided id from this function will match the id in your form.

In the view you use it like this:

@Html.ElementId(m => m.Title)

And your JS code would look like this:

var title = document.getElementById("@Html.ElementId(m => m.Title)");
var description = document.getElementById("@Html.ElementId(m => m.Description)");

A bit of mouthful, but gives you the safety net of strong types. I have not actually used it widely, so not sure how it’ll work out in the longer run.

Part 1: AspNet Identity and IoC Container Registration

Sounds like I’m making a series of articles about ASP.Net Identity and how to use it with Depenency Injection. Part 1 have seen a lot of hits from Google in just a few days. I suppose it is worth extending the tutorial.

Building up on Part 1 where I wired all Identity components to be injected by Unity container, now I’m going to add emailing service for email confirmation and password reset.

My plan is to use SendGrid as a email service and email debugging service Mailtrap.IO as a hosted fake SMTP server.

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I’m reading a lot of blogs about development and .Net. One of the blogs I read is from Jimmy Bogard and one of the recent posts there is about guidelines for using Dependency Injection container.

I got involved in comments and one of the commenters was suggesting using Func<IFoo> as injection instead of injecting the instance for IFoo. And reasons for that were:

  1. The “captive dependency” problem… objects with more constrained lifetime being held by objects with longer->lived lifetime.

  2. The (wasteful) big-bang object graph problem… when an MVC action only requires 1 dependency, but the dependency graph for all dependencies within the controller need to be resolved.

  3. The occasional property injection… when its 2am and I don’t feel like fixing a circular dependency issue (don’t hate).

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