Overview of symmetric encryption in .NET

October 21, 2017 1 Comment

Introduction

A symmetric encryption algorithm is one where the cryptographic key is the same for both encryption and decryption and is shared among the parties involved in the process.

Ideally only a small group of reliable people should have access to this key. Attackers decipher an encrypted message rather than trying to defeat the algorithm itself. The key can vary in size so the attacker will need to know this first. Once they know this then they will try combinations of possible key characters.

A clear disadvantage with this approach is that distributing and storing keys in a safe and reliable manner is difficult. On the other hand symmetric algorithms are fast.

In this short overview we’ll look at the symmetric encryption algorithms currently supported in .NET.

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Implementing the IEqualityComparer of T interface for object equality with C# .NET

October 20, 2017 Leave a comment

The generic IEqualityComparer of T provides you a way to indicate whether two custom objects are equal. We’ve looked at equality in a number of posts on this blog – see the link below if you’re curious – and IEqualityComparer fulfils a similar purpose though its usage is different.

Equality comparers are most often used to filter out duplicates from a collection.

Consider the following class:

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Implementing the IEquatable of T interface for object equality with C# .NET

October 19, 2017 1 Comment

In this short post we’ll see a way how to make two custom objects equatable using the generic IEquatable interface. Consider the following object:

public class Person
{
	public int Id { get; set; }
	public string Name { get; set; }
	public int Age { get; set; }
}

The object superclass has an Equals method that we can test as follows:

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How to declare natural ordering by implementing the generic IComparable interface in C# .NET

October 18, 2017 Leave a comment

Primitive types such as integers can be ordered naturally in some way. Numeric and alphabetical ordering comes in handy with numbers and strings. However, there’s no natural ordering for your own custom objects with a number of properties.

Consider the following Triangle class:

public class Triangle
{
	public double BaseSide { get; set; }
	public double Height { get; set; }

	public double Area
	{
		get
		{
			return (BaseSide * Height) / 2;
		}
	}
}

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How to find various machine-level system information with C# .NET

October 17, 2017 Leave a comment

The Environment class holds a range of properties that help you describe the system your app is running on. Here come some examples with inline comments:

//returns true on my PC as it is a 64-bit OS
bool is64BitOperatingSystem = Environment.Is64BitOperatingSystem;
//returns the machine name, in my case ANDRAS1
string machineName = Environment.MachineName;
			
//returns information about the operating system version, build, major, minor etc.
OperatingSystem os = Environment.OSVersion;
//returns the platform id as an enumeration, in my case it's Win32NT
PlatformID platform = os.Platform;			
//the currently installed service pack, Service Pack 1 in my case
string servicePack = os.ServicePack;
//the toString version of the OS, this is "Microsoft Windows NT 6.1.7601 Service Pack 1" on this PC
string version = os.VersionString;

//I have 4 processors on this PC
int processorCount = Environment.ProcessorCount;

//returns 2 logical drives: C: and D:
string[] logicalDrives = Environment.GetLogicalDrives();

//this is how to find all environmental variables of the system and iterate through them
IDictionary envVars = Environment.GetEnvironmentVariables();
foreach (string key in envVars.Keys)
{
	//e.g. the JAVA_HOME env.var is set to "C:\Progra~1\Java\jdk1.7.0_51\"
	Debug.WriteLine(string.Concat("key: ", key, ": ", envVars[key]));
}

//retrieve the current CLR version, in my case it's "4.0.30319.18444"
Version clrVersion = Environment.Version;

View all posts related to diagnostics here.

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Getting notified by a Windows process change in C# .NET

October 16, 2017 Leave a comment

In this post we saw an example of using the ManagementEventWatcher object and and EventQuery query. The SQL-like query was used to subscribe to a WMI – Windows Management Instrumentation – level event, namely a change in the status of a Windows service. I won’t repeat the explanation here again concerning the techniques used. So if this is new to you then consult that post, the code is very similar.

In this post we’ll see how to get notified by the creation of a new Windows process. This can be as simple as starting up Notepad. A Windows process is represented by the Win32_Process WMI class which will be used in the query. We’ll take a slightly different approach and use the WqlEventQuery object which derives from EventQuery.

Consider the following code:

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Creating a new performance counter on Windows with C# .NET

October 15, 2017 Leave a comment

In this post we saw how to list all performance counter categories and the performance counters within each category available on Windows. The last time I checked there were a little more than 27500 counters and 148 categories available on my local PC. That’s quite a lot and will probably cover most diagnostic needs where performance counters are involved in a bottleneck investigation.

However, at times you might want to create your own performance counter. The System.Diagnostics library provides the necessary objects. Here’s how you can create a new performance counter category and a counter within that category:

string categoryName = "Football";
			
if (!PerformanceCounterCategory.Exists(categoryName))
{
	string firstCounterName = "Goals scored";
	string firstCounterHelp = "Goals scored live update";
	string categoryHelp = "Football related real time statistics";
				
	PerformanceCounterCategory customCategory = new PerformanceCounterCategory(categoryName);
	PerformanceCounterCategory.Create(categoryName, categoryHelp, PerformanceCounterCategoryType.SingleInstance, firstCounterName, firstCounterHelp);
}

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Reading and clearing a Windows Event Log with C# .NET

October 14, 2017 Leave a comment

In this post we saw how to create a custom event log and here how to the write to the event log. We’ll briefly look at how to read the entries from an event log and how to clear them.

First let’s create an event log and put some messages to it:

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Writing to the Windows Event Log with C# .NET

October 13, 2017 1 Comment

In this post we saw how to create and delete event logs. We’ve also seen a couple examples of writing to the event log. Here come some more examples.

Say you want to send a warning message to the System log:

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Creating and deleting event logs with C# .NET

October 12, 2017 Leave a comment

The Windows event viewer contains a lot of useful information on what happens on the system:

Windows event viewer

Windows will by default write a lot of information here at differing levels: information, warning, failure, success and error. You can also write to the event log, create new logs and delete them if the code has the EventLogPermission permission. However, bear in mind that it’s quite resource intensive to write to the event logs. So don’t use it for general logging purposes to record what’s happening in your application. Use it to record major but infrequent events like shutdown, severe failure, start-up or any out-of-the-ordinary cases.

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