C＃正则表达式第一个单词匹配

Question

I have a string, named str, with a value of: PRINT "HELLO WORLD"

I'm trying to match it using Regex in C#, but this doesn't work:

Regex.IsMatch(str, @"^PRINT");

but if my str has a value of only PRINT , it matches.

What am I going to change in my regex expression in order to match the succeeding characters enclosed in quotation marks?

---

Edit:

I have this conditional block that is not touched when the str value is of PRINT "Hello WOrld" , but if it has PRINT , it does.

if (Regex.IsMatch(str, @"^PRINT")) {
    // some codes
}

---

Edit:

If the regex would to consider the keywork, PRINT and a block of string enclosed in quotation marks, separated by a space, what is the equivalent regex for that? Is this correct?

@"^PRINT\w+\".*\""

How to delimit the quotation marks in the regex?

Answer 1

You can escape " with "" in verbatim string..To escape " in normal string you have to use \\"

---

This would capture anything in between those two "

if (Regex.IsMatch(str, @"^PRINT")) 
{
    Regex.Match(str,@"(?<="").*?(?="")").Value;//captures content within "
}

Answer 2

From what I gather you are trying to match the following list. If you can be more explicit in what you are trying to match (more rules, etc) then making a regex for it should be fairly easy.

• starts with PRINT
• has 1+ non word character after
• has one quote
• has something (anything) after that
• has one quote
• end of line

You can try this:

var pattern = @"^PRINT[^\w]+""(.*)""$";  // you usually need those [] things :)

// * ""$ - requires the " to be at the end of the line
// * .* should match an empty quote ""
// you should trim the string on this one before matching

This is the test code that seems to show it working:

// notice that one of these has an embedded quote
var list = new [] { "PRINT", "PRINT ", "PRINT \"STUFF\"", "PRINT\t  \t\"AND \"FUN \"", " PRINT \"BAD\" " };
var pattern = @"^PRINT[^\w]+""(.*)""$";
foreach(var value in list) {
    var m = Regex.Match(value, pattern);
    if (m.Success) {
        Console.WriteLine("success: '{0}' found '{1}'", value, m.Groups[1].Value);
    } else {
        Console.WriteLine("failed:  '{0}'", value);
    }
}

And the results:

failed:  'PRINT'
failed:  'PRINT '
success: 'PRINT "STUFF"' found 'STUFF'
success: 'PRINT      "AND "FUN "' found 'AND "FUN '
failed:  ' PRINT "BAD" '

Answer 3

If your string str contains any whitespace or invisible character just before PRINT then Regex.IsMatch(str, @"^PRINT") will return false , use Regex.IsMatch(str, @"^.*PRINT") instead.

Example to extract Hello WOrld from input string:

string strInput = @" PRINT ""Hello WOrld""";
string pattern = @"^.*PRINT\s*""(?<keyword>(\s*\S+\s*)+)""";

if (Regex.IsMatch(strInput, pattern)) {
    Match m = Regex.Match(strInput, pattern);
    string extractedValue = m.Groups["keyword"].Value;
}

In verbatim string, use double quotes "" to escape single quote "

Answer 4

Regex.IsMatch（str，@“ \\ bPRINT \\ b”）;