Regex - only allow a space or nothing after a match in C#

Regex - only allow a space or nothing after a match in C#

In C#, you can use a positive lookbehind assertion in a regular expression to ensure that a match is followed by either a space or nothing. Here's an example:

string input = "Hello World! This is a test."; // Match all words that start with 'T' and are followed by either a space or nothing string pattern = @"(?<=\bT)\b\w+(?=\s|$)"; MatchCollection matches = Regex.Matches(input, pattern); foreach (Match match in matches) { Console.WriteLine(match.Value); }

In the above code, we define a regular expression pattern that uses a positive lookbehind assertion ((?<=...)) and a positive lookahead assertion ((?=...)) to match all words that start with the letter 'T' and are followed by either a space or nothing.

The positive lookbehind assertion (?<=\bT) matches the position immediately after the letter 'T', but only if it is preceded by a word boundary (\b). This ensures that we only match words that start with the letter 'T'.

The positive lookahead assertion (?=\s|$) matches either a space (\s) or the end of the line ($). This ensures that we only match words that are followed by either a space or nothing.

We use the Matches method provided by the Regex class to find all matches in the input string that match the pattern.

By using a positive lookbehind assertion in a regular expression, you can ensure that a match is followed by either a space or nothing in C#.

Examples

  1. "C# Regex - allow only space or nothing after a match"

    • Description: Search for a regex pattern in C# that ensures only a space or nothing follows a specific match.
    // Regex to allow only space or nothing after a match string inputString = "Match followed by space or nothing"; Match match = Regex.Match(inputString, @"your_pattern_here\s?");

  2. "C# Regex - enforce space or nothing after word"

    • Description: Explore how to use a regex pattern to enforce a space or nothing after a specific word in C#.
    // Regex to enforce space or nothing after a word string inputString = "Word followed by space or nothing"; Match match = Regex.Match(inputString, @"word\s?");

  3. "C# Regex - allow space or nothing after punctuation"

    • Description: Find examples of using a regex pattern in C# to allow either a space or nothing after certain punctuation marks.
    // Regex to allow space or nothing after punctuation string inputString = "Punctuation followed by space or nothing"; Match match = Regex.Match(inputString, @"[.,;:'\"]\s?");

  4. "C# Regex - restrict space or nothing after digit"

    • Description: Learn how to restrict a space or nothing after a digit using a regex pattern in C#.
    // Regex to restrict space or nothing after a digit string inputString = "Digit followed by space or nothing"; Match match = Regex.Match(inputString, @"\d\s?");

  5. "C# Regex - allow space or nothing after specific pattern"

    • Description: Explore using a regex pattern in C# to allow only a space or nothing after a specific custom-defined pattern.
    // Regex to allow space or nothing after a specific pattern string inputString = "YourPattern followed by space or nothing"; Match match = Regex.Match(inputString, @"your_pattern_here\s?");

  6. "C# Regex - space or nothing after email address"

    • Description: Find examples of using a regex pattern in C# to ensure only a space or nothing follows an email address.
    // Regex for space or nothing after an email address string inputString = "email@example.com followed by space or nothing"; Match match = Regex.Match(inputString, @"\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\s?");

  7. "C# Regex - allow space or nothing after specific character"

    • Description: Learn how to use a regex pattern in C# to allow either a space or nothing after a specific character.
    // Regex to allow space or nothing after a specific character string inputString = "SpecificCharacter followed by space or nothing"; Match match = Regex.Match(inputString, @"specific_character\s?");

  8. "C# Regex - space or nothing after URL"

    • Description: Explore using a regex pattern in C# to ensure only a space or nothing follows a URL.
    // Regex for space or nothing after a URL string inputString = "https://www.example.com followed by space or nothing"; Match match = Regex.Match(inputString, @"(https?://\S+)\s?");

  9. "C# Regex - allow space or nothing after specific keyword"

    • Description: Find examples of using a regex pattern in C# to allow either a space or nothing after a specific keyword.
    // Regex to allow space or nothing after a specific keyword string inputString = "Keyword followed by space or nothing"; Match match = Regex.Match(inputString, @"keyword\s?");

  10. "C# Regex - enforce space or nothing after specific phrase"

    • Description: Learn how to enforce either a space or nothing after a specific phrase using a regex pattern in C#.
    // Regex to enforce space or nothing after a specific phrase string inputString = "SpecificPhrase followed by space or nothing"; Match match = Regex.Match(inputString, @"specific_phrase\s?");

More Tags

android-contacts natural-sort cisco m .net-core-3.0 aspose dirname android-asynctask gatt android-typeface

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