Tips and tricks in C# .NET
July 12, 2017 Leave a comment
Say you have the following Customer object with an overridden ToString method:
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string City { get; set; }
public override string ToString()
{
return string.Format("Id: {0}, name: {1}, city: {2}", Id, Name, City);
}
}
July 11, 2017 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.
July 10, 2017 Leave a comment
There are a lot of number formats out there depending on the industry we’re looking at. E.g. negative numbers can be represented in several different ways:
…and so on. Accounting, finance and other, highly “numeric” fields will have their own standards to represent numbers. Your application may need to parse all these strings and convert them into proper numeric values. The static Parse method of the numeric classes, like int, double, decimal all accept a NumberStyles enumeration. This enumeration is located in the System.Globalization namespace.
July 7, 2017 1 Comment
Introduction
In the previous post we looked at role-based authorisation in CouchDB. With roles it’s easier to assign users as database admins, database members and read-only users than working with names only. It’s enough to assign each CouchDB user to a role and the existing authorisation rules will be applied automatically.
In this post we’ll look at how authentication works for the HTTP API using cookies.
July 6, 2017 2 Comments
There are numerous compression algorithm out there for file compression. Here come 5 examples with how-to-do links from this blog.
Compressing individual files
The following algorithms can be used to compress a single file. E.g. source.txt will be compressed to source.txt.gz.
July 5, 2017 1 Comment
Introduction
In the previous post we continued our exploration of security in CouchDB. In particular we looked at database members who have read and write access to a database. There’s no database user specifically tailored for read-only access. A more fine-grained solution is provided by update design functions where can specifically block users from modifying database documents thereby making them read-only users. This process can be difficult to manage since the update function must potentially be updated with new database members added to the list of users.
An important aspect of security in CouchDB is gradual restrictions. A CouchDB server start off its life as open to the public with no restrictions on the access rights whatsoever. We have to create a server admin and other users and then define the database admins and members for each database. Until then each database is still open to the default CouchDB user.
This is where database roles can be a better solution. That is also the main topic of this post.
July 4, 2017 1 Comment
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:
July 3, 2017 1 Comment
Introduction
In the previous post we started discussing the security features of CouchDB. An interesting feature of CouchDB is that by default, in the absence of any registered user, everyone is anonymous and all users have full access to all the parts of the Couch DB server: databases, documents, configuration, replication, everything. This is probably so that newcomers to CouchDB don’t need to spend time on security settings before getting started on its features. So the first step is to create a server administrator who then can create new users to prevent anonymous access to the server. We then created two new users, Peter and Mary, and they were promoted to database administrators to a selected database. They can now administer the database that they were assigned to. They still face various restrictions. E.g. they still cannot perform server admin tasks and they cannot delete the database they are administering.
In this post we’ll continue our discussion of this topic and concentrate on database level read and write access.
June 30, 2017 1 Comment
Introduction
In the previous post we looked at Mango operators related to arrays. With array operators such as $elemMatch, $in or $size we can write search terms related to elements in an array. Examples include searching for documents where an array field, such as “grades” includes at least one “A” or includes exactly two grades, not more or less. We’ve also seen how to dig deep into the object structure to query on elements that lie deep in the object graph, such as the price of a product of an order of a customer.
In this post we leave querying behind and start looking into some security aspects of CouchDB.
June 29, 2017 Leave a comment
Here comes a simple extension method to calculate the standard deviation of a list of integers:
public static double GetStandardDeviation(this IEnumerable<int> values)
{
double standardDeviation = 0;
int[] enumerable = values as int[] ?? values.ToArray();
int count = enumerable.Count();
if (count > 1)
{
double avg = enumerable.Average();
double sum = enumerable.Sum(d => (d - avg) * (d - avg));
standardDeviation = Math.Sqrt(sum / count);
}
return standardDeviation;
}
Here’s how you can call this method:
List<int> ints = new List<int>() { 4, 7, 3, 9, 13, 90, 5, 25, 13, 65, 34, 76, 54, 12, 51, 23, 3, 1, 7 };
double stdev = ints.GetStandardDeviation();
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