Gain insights into pattern matching with regular expressions in C#. Explore data validation, information extraction, and more using String and Regex APIs with practical examples.

Regular expressions provide an extremely powerful method for pattern matching with strings. They are very useful for parsing information like dates, phone numbers, or zip codes from important text files, such as code files, log files, spreadsheets, or documents. The course discusses everyday use cases of regular expressions, e.g., data validation, information extraction, pattern matching, and search and replace.

This course will teach you the core concepts of pattern matching, character classes, special and meta characters, and quantifiers. You will also learn conditional regular expressions including lookahead and lookbehind assertions. You will also learn the APIs used in C# for regular expressions with hands-on code widgets. 

This course will teach you how to perform pattern matching with a regular expression using String and Regex APIs for the above-mentioned practical use cases in C#.

Tarun Telang

Tarun Telang is a passionate software engineer, leader, architect, author, and active contributor in various online technical forums.

C# and Microsoft Expert

Working with Regular Expressions in C#

# Using invariant culture with regular expressions


When we perform operations using regular expressions, such as `Replace` and `Match`, the current thread’s culture determines the **invariant culture**.

The invariant culture is a `CultureInfo` object that represents a culture that’s not influenced by the user’s regional settings.

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The following code shows how to set the current thread’s culture to the invariant culture:

```
Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
```

The following code shows how to set the current thread’s UI culture to the invariant culture:


```
Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;
```

>**Note**: Setting the current thread’s culture or UI culture to the invariant culture only affects the current thread. Other threads in the same process are not affected.

If we use regular expressions in a multithreaded application, we should set the current thread’s culture and UI culture to the invariant culture before we call any methods that use regular expressions. This ensures that the results of the regular expression operations are consistent across all threads.

# Security considerations



Regular expressions are powerful tools that provide a great deal of flexibility when working with strings. However, this flexibility comes at a cost. Regular expressions are more complex than simple string operations, and can take longer to execute.

When working with regular expressions, it is important to be aware of potential security issues. A malicious user could potentially exploit a regular expression to gain access to sensitive information, or launch a denial of service attack.




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Learn advanced topics of invariant culture, testing for correctness, performance, and security considerations with regular expressions.

Introduction

Building Blocks of .NET Regular Expressions

Advanced Concepts

Course Wrap Up

Advanced Topics in Regular Expressions

Using invariant culture with regular expressions