Determine if all elements fulfil a condition in a sequence with LINQ C#

March 15, 2017 Leave a comment

Say we have the following string list:

string[] bands = { "ACDC", "Queen", "Aerosmith", "Iron Maiden", "Megadeth", "Metallica", "Cream", "Oasis", "Abba", "Blur", "Chic", "Eurythmics", "Genesis", "INXS", "Midnight Oil", "Kent", "Madness", "Manic Street Preachers"
, "Noir Desir", "The Offspring", "Pink Floyd", "Rammstein", "Red Hot Chili Peppers", "Tears for Fears"
, "Deep Purple", "KISS"};

Say we’d like to determine if all elements in the sequence fulfil a certain condition. Nothing could be easier using the All operator:

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Determine if a sequence contains a certain element with LINQ C#

March 14, 2017 Leave a comment

Say we have the following string list:

string[] bands = { "ACDC", "Queen", "Aerosmith", "Iron Maiden", "Megadeth", "Metallica", "Cream", "Oasis", "Abba", "Blur", "Chic", "Eurythmics", "Genesis", "INXS", "Midnight Oil", "Kent", "Madness", "Manic Street Preachers"
, "Noir Desir", "The Offspring", "Pink Floyd", "Rammstein", "Red Hot Chili Peppers", "Tears for Fears"
, "Deep Purple", "KISS"};

If you’d like to check if a certain string element is present in the sequence then you can use the Contains operator in LINQ:

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Introduction to ASP.NET Core part 23: the EntityFramework repository

March 13, 2017 Leave a comment

Introduction

In the previous post we started looking into EntityFramework Core. We saw how to install and wire up EF Core using NuGet and Startup.cs. We also discussed the basics of creating a DB context class with a single DB set of the Book domain. The Update-Database command in the package manager detects our DB context class in the project and creates a data migration file. The console also enabled us to create the database and the Books table table using code-first and EF data migrations with the help of the generated migration class. That’s where we can declare in code what type of objects we want to create in the database: tables, indexes, primary keys etc.

The next step is to actually use this database in our demo book store project. We’ll do that in this post.

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Creating list ranges in F#

March 12, 2017 Leave a comment

We can easily create a list of integers in F# with a start and end value as follows:

let myRangeList = [1..10]

myRangeList will contain the integers from 1 to 10:

int list = [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]

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Tuples in F#

March 11, 2017 1 Comment

Tuples are collections where each element can be of different type. If you have a C# or Python background then you must be familiar with tuples. A tuple can be used to return multiple values from a function without having to declare an object for it.

Here’s a tuple with 5 elements:

let addThreeNumbers x y z = x + y + z
let myFirstTuple = (45, "hello world", 5., true, addThreeNumbers)

This tuple has an integer, a string, a float, a boolean and a function in it.

val myFirstTuple : int * string * float * bool * (int -> int -> int -> int) = (45, “hello world”, 5.0, true, )

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Finding the set difference between two sequences using the LINQ Except operator

March 10, 2017 Leave a comment

Say you have the following two sequences:

string[] first = new string[] {"hello", "hi", "good evening", "good day", "good morning", "goodbye" };
string[] second = new string[] {"whatsup", "how are you", "hello", "bye", "hi"};

If you’d like to find the values that only figure in “first” then it’s easy to achieve using the LINQ Except operator:

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Introduction to ASP.NET Core part 22: wiring up EntityFramework Core

March 9, 2017 Leave a comment

Introduction

In the previous post we looked at a new feature in .NET Core called view components. A view component is sort of a mixture between full-blown controllers and partial views. It has its own controller and view but is supposed to be viewed and invoked within a parent view. A view component controller can have its own dependencies injected into it via its constructor just like in the case of “real” controllers. It is a normal C# class which can have its own functions and input parameters. We can implement either the Invoke or InvokeAsync function to return a view depending on whether we want to execute the view component asynchronously or not. The view returned by a view component controller is a cshtml file which will be rendered within a parent view. Thus a view component offers a lot more flexibility than a partial view when breaking out a smaller part of a view.

In this post we’ll start looking at EntityFramework Core which will provide a data store to our application.

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Performing joins across two sequences with the LINQ Join operator

March 8, 2017 Leave a comment

With the Join operator in LINQ you can perform joins similar to using the JOIN keyword in SQL: the result will be a join on two sequences based on some common key.

We’ll use the following data structures:

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Projection in LINQ C# with the Select operator

March 7, 2017 Leave a comment

You can use the Select() extension method in LINQ to create an output of type T from an input sequence of type other than T. Let’s see some examples:

Source data:

string[] bands = { "ACDC", "Queen", "Aerosmith", "Iron Maiden", "Megadeth", "Metallica", "Cream", "Oasis", "Abba", "Blur" , "Chic", "Eurythmics", "Genesis", "INXS", "Midnight Oil", "Kent", "Madness", "Manic Street Preachers", "Noir Desir", "The Offspring", "Pink Floyd", "Rammstein", "Red Hot Chili Peppers", "Tears for Fears", "Deep Purple", "KISS"};

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Introduction to ASP.NET Core part 21: view components

March 6, 2017 3 Comments

Introduction

In the previous post we looked at partial views. Partial views have been around for a long time in ASP.NET MVC and they work in much the same way in .NET Core MVC. Partial views are a means of factoring out parts of a view into smaller, reusable and more manageable units. Partial views can also have their own dependencies. So they behave just like “full” views but are meant to be rendered within a parent view.

In this post we’ll look at an alternative to partial views called view components. View components are new in this version of MVC.

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