Скачать или смотреть How to Achieve Exact String Matching Using Regular Expressions in C#

Learn how to properly use Regular Expressions in C# to match exact strings like "test", and avoid common pitfalls.
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Understanding Exact String Matching with Regular Expressions in C#

When working with Regular Expressions (regex), you may find yourself needing to match an exact string. The challenge can arise with regex syntax and formatting, especially if you're not familiar with the specifics of the programming language you're using. In this guide, we'll explore how to effectively match an exact string in C# using regex, particularly focusing on the common issue that leads to unexpected false results.

The Problem: Matching an Exact String

Suppose you want to check if the string "test" is matched in various contexts. According to your criteria:

Should match: "test", "test new", "new test"

Should not match: "testtt"

To formulate this requirement, you were attempting to use the following regular expression in C# :

[[See Video to Reveal this Text or Code Snippet]]

However, you didn't receive the results you expected. Let's understand why and how to fix it.

Breaking Down the Regex Issue

This stems from a misunderstanding in how regex patterns are framed in C# . Here's why your initial regex didn't work:

Accessing the String: The outer slashes / are commonly used in some programming languages (like JavaScript) to denote regular expressions. In C# , you don't use these slashes. This means that C# is interpreting this regex as a literal string /test/, rather than as the pattern test you were aiming for.

Boundary Assertions: Your use of \b was correct; it indicates a word boundary. This is what helps you ensure that "test" is matched only when it's a complete word, not part of another word (like "testtt").

Implementing the Correct Solution

To match the string "test" correctly in C# , you need to revise the regex expression. Here's how you do it:

Remove the Slashes: Eliminate the forward slashes from the expression.

Use Proper Syntax: The correct syntax in C# would just be the regex pattern itself, with the right boundary assertions.

Corrected Regex Example

Here is the revised regex expression you should use:

[[See Video to Reveal this Text or Code Snippet]]

Practical Example

Here's how you might use it in a C# application:

[[See Video to Reveal this Text or Code Snippet]]

Expected Output

When you run this code, you should see output indicating which strings match the exact word "test":

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Matching exact strings using Regular Expressions in C# can be straightforward once you understand the specifics of syntax and the necessary components. By removing the unnecessary forward slashes and correctly implementing the regex pattern, you'll be able to effectively identify exact matches in your strings.

Now you can confidently apply this knowledge to your projects and avoid the common pitfalls associated with regex in C# !