How can I replace part of a string that has a potentially unknown starting index. For instance, if I had the following strings:
"<sometexthere width='200'>"
"<sometexthere tile='test' width='345'>"
I would be looking to replace the width attibute value that can have an unknown value and as mentioned before an unknown start index.
The I understand that I would somehow have to base this on the following part, which is constant, I just don't quite understand how to achieve this.
width='
So far you've got seven answers telling you to do the wrong thing. Do not use regular expressions to do the job of a parser. I am assuming that your string is a hunk of markup. Let's suppose it is HTML. What does your regular expression do with:
<html>
<script>
var width='100';
</script>
<blah width =
'200'>
... and so on ...
I'd be willing to bet as much as a dollar that it replaces the JScript code, which it should not, and does not replace the attribute of the blah tag -- it is perfectly legal to have whitespace in an attribute.
If you have to parse a markup language then parse the markup language. Get yourself a parser and use it; that's what parsers are for.
Take a look at the Regex class, you can search for the content of the attribute and repalce the value with this class.
Off the cuff Regex.Replace might do the trick:
var newString = Regex.Replace(@".*width='\d'",string.Foramt("width='{0}'",newValue));
using System.Text.RegularExpressions;
Regex reg = new Regex(@"width='\d*'");
string newString = reg.Replace(oldString,"width='325'");
This will return a new string with a new width, provided you put a number between the ' ' in the new width field.
Use the regular expression
Regex regex = new Regex(@"\b(width)\b\s*=\s*'d+'");
where the \bs indicate that you wish to match a whole word, \s* allows for zero or any number of whitespace charaters and \d+ allows for one or more numeric placeholder. To replace the numeric value you can then use:
int nRepValue = 400;
string strYourXML = "<sometexthere width='200'>";
// Does the string contain the width?
string strNewString = String.Empty;
Match match = regex.Match(strYourXML);
if (match.Success)
strNewString =
regex.Replace(strYourXML, String.Format("match='{0}'", nRepValue.ToString()));
else
// Do something else...
Hope this helps.
You can use a regular expression (RegEx) to find and replace all the text in single quotes after "width=".
You could use a regular expression, like (?<=width=')(\d+)
Example:
var replaced = Regex.Replace("<sometexthere width='200'>", "(?<=width=')(\\d+)", "123");"
replaced is now: <sometexthere width='123'>
I would use a Regex.
Something like this to replace the width value with 123456.
string aString = "<sometexthere tile='test' width='345'>";
Regex regex = new Regex("(?<part1>.*width=')(?<part2>\\d+)(?<part3>'.*)");
var replacedString = regex.Replace(aString, "${part1}123456${part3}");
Use regular expressions to achieve this:
using System.Text.RegularExpressions;
...
string yourString = "<sometexthere width='200'>";
// updates width value to 300
yourString = Regex.Replace(yourString , "width='[^']+'", width='300');
// replaces width value with height value of 450
yourString = Regex.Replace(yourString , "width='[^']+'", height='450');
