Listing all performance counters on Windows with C# .NET

August 1, 2017 Leave a comment

Performance counters in Windows can help you with finding bottlenecks in your application. There’s a long range of built-in performance counters in Windows which you can view in the Performance Monitor window:

Performance Monitor window

Right-click anywhere on the larger screen to the right and select Add Counters to add your counters to the graph. The Add Counters window will show the categories first. You can then open a category and select one or more specific counters within that category. The graph will show the real-time data immediately:

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4 ways to enumerate processes on Windows with C# .NET

July 31, 2017 Leave a comment

The Process object in the System.Diagnostics namespace refers to an operating-system process. This object is the entry point into enumerating the processes currently running on the OS.

This is how you can find the currently active process:

Process current = Process.GetCurrentProcess();
Console.WriteLine(current);

…which will yield the name of the process running this short test code.

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Using the let keyword in .NET LINQ to store variables within a statement

July 28, 2017 Leave a comment

It happens that we have a LINQ statement where we want to refer to partial results by variable names while expressing some computation. The “let” keyword lets us do that. Those who are familiar for the F# language already know that “let” is an important keyword to bind some value to a variable.

Suppose we have the following list of integers:

List<int> integers = new List<int>()
{
	5, 7, 4, 6, 10, 4, 6, 4, 5, 12
};

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Hashing passwords with a password based key derivation function in .NET

July 27, 2017 Leave a comment

In this post we saw a basic hashing technique using a password and a salt. We added an extra random set of bytes to the password and hashed the combined byte array instead of just the password bytes. We can store the salt along with the hash in our database. The main purpose of adding a salt to the password is to increase its entropy which more or less means randomness.

Hashing the password with an extra salt like that may still not be as secure as we think it is. The processing power of today’s fast computers and the increasing size of available rainbow tables keep pushing the limits of what’s available to crack with brute force attacks. One way to increase the difficulty of cracking a password is to keep hashing its hash in an iterative manner. Password-based key derivation functions help us achieve that and we’ll see an example of their usage in this post.

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Checking for arithmetic overflow in C# .NET

July 26, 2017 Leave a 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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Searching for elements in arrays in C# .NET

July 25, 2017 Leave a comment

The Array class has a number of useful static methods. A group of them is used for searching purposes. The method names are generally quite descriptive. Here are some them with comments in the code:

string[] bands = new string[6] { "Queen", "ACDC", "Metallica", "Genesis", "INXS", "Motörhead" };

//find the first entry in the array which starts with Q, finds "Queen"
string firstBandStartingWithQ = Array.Find<string>(bands, s => s.StartsWith("Q"));
//finds last entry start with M, finds Motörhead
string lastBandStartingWithM = Array.FindLast<string>(bands, s => s.StartsWith("M"));
//finds Metallica and Motörhead and puts them in an array
string[] allWithM = Array.FindAll<string>(bands, s => s.StartsWith("M"));
//index will be 0 as Queen is the first item in the array
int queenIndex = Array.FindIndex<string>(bands, s => s == "Queen");
//yields true as ACDC figures in the array
bool acdIsThere = Array.Exists<string>(bands, s => s == "ACDC");

View all various C# language feature related posts here.

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Extension methods in C#

July 24, 2017 1 Comment

Introduction

Extension methods in C# allow you to extend the functionality of types that you didn’t write and don’t have direct access to. They look like integral parts of any built-in classes in .NET, e.g.:

DateTime.Now.ToMyCustomDate();
string.ToThreeLetterAbbreviation();

You can extend the following types in C#:

  • Classes
  • Structs
  • Interfaces

You can extend public types of 3rd party libraries. You can also extend generic types, such as List of T and IEnumerable of T. You cannot extend sealed classes.

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Introduction to CouchDB with .NET part 25: connecting to CouchDB from .NET

July 21, 2017 4 Comments

Introduction

In the previous post we looked at how cookie based authentication works in the CouchDB API. This type of authentication follows a popular model in APIs. The user of the API will first need to acquire a temporary authentication cookie or token. This token must then be attached to the subsequent calls to the API as a means of authentication without sending the username and password in the request. Authentication cookies typically have an expiration date of some minutes. In CouchDB this is set to 10 minutes by default.

In this post we’ll look at how to connect to CouchDB from a .NET project. This is also the final post in this introductory series.

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Replacing substrings using Regex in C# .NET: date format example

July 17, 2017 Leave a comment

Say your application receives the dates in the following format:

mm/dd/yy

…but what you actually need is this:

dd-mm-yy

You can try and achieve that with string operations such as IndexOf and Replace. You can however perform more sophisticated substring operations using regular expressions. The following method will perform the required change:

private static string ReformatDate(String dateInput)
{
	return Regex.Replace(dateInput, "\\b(?<month>\\d{1,2})/(?<day>\\d{1,2})/(?<year>\\d{2,4})\\b"
		, "${day}-${month}-${year}");
}

Calling this method with “10/28/14” returns “28-10-14”.

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Replacing substrings using Regex in C# .NET: string cleaning example

July 14, 2017 Leave a comment

We often need to sanitize string inputs where the input value is out of our control. Some of those inputs can come with unwanted characters. The following method using Regex removes all non-alphanumeric characters except for ‘@’, ‘-‘ and ‘.’:

private static string RemoveNonAlphaNumericCharacters(String input)
{
	return Regex.Replace(input, @"[^\w\.@-]", string.Empty);
}

Calling this method like…

string cleanString = RemoveNonAlphaNumericCharacters("()h{e??l#'l>>o<<");

…returns “hello”.

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