The CASE statement in SQL allows you to implement conditional logic within queries, making it a powerful tool for handling complex data transformations and classifications.
CASE
The CASE statement works like an IF-ELSE structure, evaluating conditions and returning corresponding values:
IF-ELSE
SELECT column_name, CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE default_result END AS alias_name FROM table_name;
Assume we have an Employees table with an Age column, and we want to categorize employees based on their age groups:
Employees
Age
SELECT Name, Age, CASE WHEN Age < 25 THEN 'Young' WHEN Age BETWEEN 25 AND 40 THEN 'Mid-Age' ELSE 'Senior' END AS AgeCategory FROM Employees;
CASE is often used in aggregate functions to perform conditional counting or summing:
SELECT SUM(CASE WHEN Age < 25 THEN 1 ELSE 0 END) AS YoungCount, SUM(CASE WHEN Age BETWEEN 25 AND 40 THEN 1 ELSE 0 END) AS MidAgeCount, SUM(CASE WHEN Age > 40 THEN 1 ELSE 0 END) AS SeniorCount FROM Employees;
You can use CASE to customize sorting order dynamically:
SELECT Name, Age FROM Employees ORDER BY CASE WHEN Age < 25 THEN 1 WHEN Age BETWEEN 25 AND 40 THEN 2 ELSE 3 END;
The CASE statement is a versatile tool in SQL for implementing conditional logic in SELECT, WHERE, ORDER BY, and aggregate functions. It enhances query flexibility, making data classification and transformation more efficient.
SELECT
WHERE
ORDER BY
XML (Extensible Markup Language) is a widely used format for storing and transporting data.
In C#, you can create XML files efficiently using the XmlWriter and XDocument classes. This guide covers both methods with practical examples.
XmlWriter
XDocument
XmlWriter provides a fast and memory-efficient way to generate XML files by writing elements sequentially.
using System; using System.Xml; class Program { static void Main() { using (XmlWriter writer = XmlWriter.Create("person.xml")) { writer.WriteStartDocument(); writer.WriteStartElement("Person"); writer.WriteElementString("FirstName", "John"); writer.WriteElementString("LastName", "Doe"); writer.WriteElementString("Age", "30"); writer.WriteEndElement(); writer.WriteEndDocument(); } Console.WriteLine("XML file created successfully."); } }
Output (person.xml):
person.xml
<?xml version="1.0" encoding="utf-8"?> <Person> <FirstName>John</FirstName> <LastName>Doe</LastName> <Age>30</Age> </Person>
The XDocument class from LINQ to XML provides a more readable and flexible way to create XML files.
using System; using System.Xml.Linq; class Program { static void Main() { XDocument doc = new XDocument( new XElement("Person", new XElement("FirstName", "John"), new XElement("LastName", "Doe"), new XElement("Age", "30") ) ); doc.Save("person.xml"); Console.WriteLine("XML file created successfully."); } }
This approach is ideal for working with complex XML structures and integrating LINQ queries.
Writing XML files in C# is straightforward with XmlWriter and XDocument. Choose the method that best suits your needs for performance, readability, and maintainability.
When working with URLs in C#, encoding is essential to ensure that special characters (like spaces, ?, &, and =) don’t break the URL structure. The recommended way to encode a string for a URL is by using Uri.EscapeDataString(), which converts unsafe characters into their percent-encoded equivalents.
string rawText = "hello world!"; string encodedText = Uri.EscapeDataString(rawText); Console.WriteLine(encodedText); // Output: hello%20world%21
This method encodes spaces as %20, making it ideal for query parameters.
For ASP.NET applications, you can also use HttpUtility.UrlEncode() (from System.Web), which encodes spaces as +:
using System.Web; string encodedText = HttpUtility.UrlEncode("hello world!"); Console.WriteLine(encodedText); // Output: hello+world%21
For .NET Core and later, Uri.EscapeDataString() is the preferred choice.
In C#, you can format an integer with commas (thousands separator) using ToString with a format specifier.
int number = 1234567; string formattedNumber = number.ToString("N0"); // "1,234,567" Console.WriteLine(formattedNumber);
Explanation:
"N0": The "N" format specifier stands for Number, and "0" means no decimal places. The output depends on the culture settings, so in regions where , is the decimal separator, you might get 1.234.567.
Alternative:
You can also specify culture explicitly if you need a specific format:
using System.Globalization; int number = 1234567; string formattedNumber = number.ToString("N0", CultureInfo.InvariantCulture); Console.WriteLine(formattedNumber); // "1,234,567"
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