Type conversion example in C# .NET using the IConvertible interface

April 22, 2015 2 Comments

In this we saw how to convert between numeric types explicitly and implicitly. There are other ways to implement conversions in C#. You must have come across the System.Convert static methods such as System.ConvertToInt32 or System.ConvertToByte.

You can implement your own conversions by implementing the IConvertible interface. Consider the following object:

public class House
{
	public double Area { get; set; }
	public int NumberOfRooms { get; set; }
	public string Address { get; set; }
	public bool ForSale { get; set; }
        public DateTime DateBuilt { get; set; }
}

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Overriding explicit and implicit conversion in C# .NET

April 21, 2015 3 Comments

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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Randomly rearrange a string in .NET C#

April 17, 2015 2 Comments

Say you’d like to randomly rearrange the contents of a string, i.e. put the constituent characters into new, random positions. The following method can help you with that using a combination of LINQ and Random:

private static string RearrangeString(string startingPoint)
{
	Random num = new Random();
	string rand = new string(startingPoint.
		OrderBy(s => (num.Next(2) % 2) == 0).ToArray());
	return rand;
}

Let’s test it with my name:

string myName = "Andras Nemes";
string myNewName = RearrangeString(myName);

So my new name can be something like “drsNeeAna ms” or “AdaNmesnrs e” or even “ArsNmenda es”, I haven’t decided yet.

Filip Ekberg drew my attention to the following alternative solution:

string rand = new string(startingPoint.OrderBy(x => Guid.NewGuid()).ToArray());

View the list of posts on LINQ here.

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Using Amazon RedShift with the AWS .NET API Part 10: RedShift in Big Data

April 16, 2015 Leave a comment

Introduction

In the previous post we discussed how to calculate the more complex parts of the aggregation script: the median and nth percentile if the URL response time.

This post will take up the Big Data thread where we left off at the end of the series on Amazon S3. We’ll also refer to what we built [at the end of the series on Elastic MapReduce]. That post took up how to run an aggregation job via the AWS .NET SDK on an available EMR cluster. Therefore the pre-requisite of following the code examples in this post is familiarity with what we discussed in those topics.

In this post our goal is to show an alternative to EMR. We’ll also see how to import the raw data source from S3 into RedShift.

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Breaking up a collection into smaller fixed size collections with C# .NET

April 15, 2015 3 Comments

Occasionally you may need to break up a large collection into smaller size collections or groups. Consider the following integer list:

List<int> ints = new List<int>() { 1, 4, 2, 5, 2, 6, 5, 43, 6, 234, 645, 2, 12, 45, 13, 5, 3 };

The goal is to break up this list into groups of size 5 and if necessary an additional list for the remaining elements. The following generic method will do the trick:

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5 ways to concatenate strings with C# .NET

April 14, 2015 1 Comment

There are multiple ways to build a string out of other strings in .NET. Here come 5 of them.

Let’s start with the most obvious one that language learners encounter first, i.e. concatenation done by the ‘+’ operator:

string concatenatedOne = "This " + "is " + "a " + "concatenated " + "string.";

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Using Amazon RedShift with the AWS .NET API Part 9: data warehousing and the star schema 3

April 13, 2015 1 Comment

Introduction

In the previous post we started formulating a couple of Postgresql statements to fill in the dimension tables and the aggregation values. We saw that it wasn’t particularly difficult to calculate some basic aggregations over combinations of URL and Customer. We ignored the calculation of the median and percentile values and set them to 0. I’ve decided to dedicate a post just for those functions as I thought they were a lot more complex than min, max and average.

Median in RedShift

Median is also a percentile value, it is the 50th percentile. So we could use the percentile function for the median as well but median has its own dedicated function in RedShift. It’s not a compact function, like min() where you can pass in one or more arguments and you get a single value.

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Combinable enumerations in C# .NET

April 10, 2015 Leave a comment

You’ve probably encountered cases with combined enum values using the pipe character, i.e. the “bitwise or” operator ‘|’:

Size.Large | Size.ExtraLarge

Let’s see an example of how to create such an enum.

The enumeration is decorated with the Flags attribute like in the following example:

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Using Amazon RedShift with the AWS .NET API Part 8: data warehousing and the star schema 2

April 9, 2015 1 Comment

Introduction

In the previous post we discussed the basics of data warehousing and the different commonly used database schemas associated with it. We also set up a couple of tables: one raw data table which we filled with some raw data records, two dimension tables and a fact table.

In this post we’ll build upon the existing tables and present a couple of useful Postgresql statements in RedShift. Keep in mind that Postgresql in RedShift is very limited compared to the full version so you often need to be resourceful.

Fill in the dimension tables

Recall that we have 2 dimension tables: DimUrl and DimCustomer. Both are referenced from the fact table by their primary keys. We haven’t added any data into them yet. We’ll do that now.

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How to pass any number of parameters into a method in C# .NET

April 8, 2015 1 Comment

You must have come across built-in methods in .NET where you can send any number of arguments into a method. E.g. string.Format has an overload where you can pass in a format string and then an array with the “params” modifier.

There’s nothing stopping you from using the same keyword to write a similar method, here’s an example:

public void MethodWithParams(int toBeMultiplied, params int[] multipliers)
{
	foreach (int m in multipliers)
	{ 
		Console.WriteLine(string.Format("{0} x {1} = {2}", toBeMultiplied, m, toBeMultiplied * m));
	}
}

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