Regex to match "True" or "False"

I need to create Regular Expression validator which will need to match a text "True" or "False" (Case Insensitive).

I have tried the following regex

^(True|False|TRUE|FALSE)$

Is this correct? but there is problem in Case Sensitive.

Edit

I have tried regex in following answers but it's not firing, because of ?i

0

5 Answers

Either use RegexOptions.IgnoreCase

or the inline ?i modifier

^(?i)(true|false)$

1

I have checked all the answers in this post but nothing worked as expected.

I Guess ?i is not supported in Asp.Net RegularExpression validator.

Finally I used following regex.

^([Tt][Rr][Uu][Ee]|[Ff][Aa][Ll][Ss][Ee])$

It worked as expected.

This regex will be used for dynamically created Asp.net RegularExpressionvalidator.

7

With a small optimization:

^(?:tru|fals)e$

Since (?i) is not validating, we'll set the case insensitivity in the code.

For any future reader who needs the code:

Dim FoundMatch As Boolean
Try FoundMatch = Regex.IsMatch(SubjectString, "^(?:tru|fals)e$", RegexOptions.IgnoreCase)
Catch ex As ArgumentException 'Syntax error in the regular expression
End Try

3

Use RegexOptions.IgnoreCase option and use the below regex:

^(true|false)$

or use ignore case modifer ?i

Like this:

^(?i:true|false)$

Another option would be to convert the string to lower case and just use ^(true|false)$

1

Another approach for words True or False:

If Boolean.TryParse(yourString, New Boolean) = true Then 'ok
else 'not ok
End If

If you want convert text to boolean variable and use it later:

Dim value As Boolean
If Boolean.TryParse(yourString, value) = true Then 'Use value
else 'Handle a wrong text situation
End If

Boolean.TryParse ignore case. trUe or TRUE parsed ok

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