Checking for arithmetic overflow in C# .NET

December 16, 2015 1 Comment

As you know primitive numeric types in C# – and other modern programming languages – have maximum and minimum values that can be stored in memory. If you’re trying to store a larger number in the variable then you’ll get an overflow with unexpected results.

Let’s see an example with the “byte” type. It is actually not one of the primitive types, like int or long, but simply a keyword for an integral type to store the numbers 0-255. Why 255? 1 byte consists of 8 bits and 8 bits in the computer’s memory allows us to store 255 as the highest number. 255 in binary is all 1’s for all 8 bits:

11111111

What happens if we add 1 to that? On paper we can easily solve it by some basic binary maths:

11111111
+ 00000001
===========
100000000

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Overriding explicit and implicit conversion in C# .NET

December 15, 2015 1 Comment

Custom implicit and explicit conversions for numeric types can be defined in C# quite easily. You need to be aware of the “implicit”, “explicit” and “operator” keywords.

Consider the following class:

public class Measurement
{
	public int Value { get; set; }
}

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Domain Driven Design with Web API extensions part 11: the MongoDb database objects

December 14, 2015 Leave a comment

Introduction

In the previous post we mainly discussed the advantages and limitations of coding against MongoDb using .NET. We also discussed the MongoDb context a little bit and started building the MongoDb version of the repository. We said that there’s not much automation available in the .NET MongoDb driver compared to what you get in EF. However, that’s not necessarily a bad thing since you’re not tied to some “secret” and “magic” underlying mechanism that does a lot of work in the background. Instead you’re free to implement the objects, the rules, the conversions etc. as you wish. It usually means more code, but you get absolute freedom for your repository implementation in return.

In this post we’ll first add a new element to the common infrastructure layer. Then we’ll add the MongoDb database representation of our domain objects.

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Projection in LINQ C# with the Select operator

December 11, 2015 1 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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Domain Driven Design with Web API extensions part 10: the MongoDb context

December 10, 2015 Leave a comment

Introduction

In the previous post we installed MongoDb locally. We also started the MongoDb server and connected to it with a client. We then inserted a test console application into our DDD skeleton project, imported the MongoDb .NET driver and connected to the MongoDb server using the driver.

In this post we’ll continue to explore the MongoDb context and some practical limitations compared to the automated tools available in EntityFramework. We’ll also add a new C# console library to the DDD skeleton project. The new library will eventually contain the MongoDb equivalent classes of what we have in the WebSuiteDemo.Loadtesting.Repository.EF layer.

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Customise your list by overriding Collection of T with C# .NET

December 9, 2015 Leave a comment

Imagine that you’d like to build a list type of collection where you want to restrict the insertion and/or deletion of items in some way. Let’s say we need an integer list with the following rules:

  • The allowed range of integers is between 0 and 10 inclusive
  • A user should not be able to remove an item at index 0
  • A user should not be able to remove all items at once

One possible solution is to derive from the Collection of T class. The generic Collection of T class in the System.Collections.ObjectModel namespace provides virtual methods that you can override in your custom collection.

The virtual InsertItem and SetItem methods are necessary to control the behaviour of the Collection.Add and the way items can be modified through an indexer:

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Resolving null values in C#

December 8, 2015 1 Comment

Say you have a method which accepts a string parameter. The method may need to handle null values in some way. One strategy is to validate the parameter and throw an exception:

private static string Resolve(string input)
{
	if (input == null) throw new ArgumentNullException("Input");
.
.
.
}

Another strategy is to provide some default value with an if-else statement:

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Domain Driven Design with Web API extensions part 9: setting up MongoDb

December 7, 2015 1 Comment

Introduction

In the previous post we set out the main topic of this new extension to the DDD model project. We said that we would add another repository mechanism, namely MongoDb. We went through the basic idea and some terminology behind MongoDb, e.g. what a document, a collection or an object ID means.

In this post we’ll set up MongoDb locally and try to connect to it from .NET using the MongoDb .NET driver.

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How to create custom string formatters with C# .NET

December 4, 2015 Leave a comment

.NET has a fairly large number of built-in string formatters that you can pass into the string.Format method. Here are some examples from the MSDN page about formatting:

String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
                                city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
                                (city.Item5 - city.Item3)/ (double)city.Item3);
String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}\n",
                                    "City", "Year", "Population", "Change (%)");
String.Format("{0,-10:C}", 126347.89m);

The IFormatProvider and ICustomFormatter interfaces will provide you with the methods required to create your own formats.

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Domain Driven Design with Web API extensions part 8: domain repository with MongoDb

December 3, 2015 1 Comment

Introduction

Some months ago we went through an updated series on Domain Driven Design starting with this post. We built a functioning skeleton project with EntityFramework as the backing store, a Web API layer as the top consumer, a loosely coupled service layer and a central domain layer with some logic.

In this extension series we’ll investigate how to implement the domain repository in a data store that’s markedly different from SQL Server. In particular we’ll take a look at the NoSql document-based MongoDb.

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