Add context to IEnumerable<> elements

Elements of an IEnumerable sequence do not know about the other elements. I often need to compare an element with a previous or next element. Sometimes I need other context like all the other elements, the previous elements or if an element is the last element. That is why I use an extension method that adds context to all elements.

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Paging with Linq to objects

Paging with Linq (to objects) seems quite simple: This is handy when you need a page 'in the middle only' but if you need to enumerate all pages, you have to caculate the number of pages yourself. The next method will help you to get all pages:

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Ultimate command line arguments parsing: query with Linq

Command line parsing in C# is (static void Main(args []string) is very limited. That is why I created a ParameterParser class that results a list of Parameter objects that can be queried with Linq. An example:

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Create your own navigation system (with a Graph, Node and Connection class)

Lots of people uses naviagtion systems like TomTom these days. As a C# deveoper you might want to know what the basic principles are behind these systems. This post shows you 3 fully functional classes behind the principles of a navigation system.

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Permutations and missing values, helpful with unit testing

Creating of unit tests of a method with 1 bool parameter needs at least 2 unit tests (false and true). But how many unit tests do you need for a parameter of type IEnumerable? A variant of the Permutations() method will help you to create almost all necessary combinations with just one extension method!

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A SOLID validation class

A long story today, but very instructive if you do not have much experience with SOLID. I will give you 2 clues in advance:

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LazyList<T>: A better LINQ-result-cache than List<T>

While designing a new programming language, I wondered if I would cache query results by default or not. Caching has advantages and disadvantages. I Found a solution that has the best of both worlds. The solution is also possible in C#!

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Except, intersect and union without distinct

Immaging that you have a customer that should pay you €10, €10, €20, €30, €30. He already paid you €10, €20. You need to know what he still needs to pay you. How will C#/LINQ helps you to give the answer?

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A generic tree of nodes, the easy way!

Today I saw a Stackoverflow-post about a genaral solution for tree and nodes. It reminds me of a solution I created to store departments in tree. I was surprised that no standard .NET collection does exactly what I need, so I created my own Node. It has properties like:

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Any, Single, Multiple and Count

In a collection we can easily check if there is any (particular) item: This is a very efficient way to check because it doesn't enumerate the whole collection. After enumerating the first element, the Any() method returns the result. This saves time if the collection is large or enumeration goes slow.

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Enum to dictionary

In a previous project we stored the values of an enum in a database. That made it easy to fill listboxes and comboboxes. It also helps to ensure data integrity. Storing enums means a violations of the most important rule for developers: single point of definition.

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