Replace string between strings

Question

In c#, I am trying to replace any string between two given strings, primarily using Regex. For example, if I have:

TextBlock Text="this is a test"

Then I want to change it to:

TextBlock Text="Any given string comes here"

For that, after some search, I tried this method:

Regex.Replace(inputString, @"(?<=TextBlock Text=\")(\w+?)(?=\")", "Any given string comes here");

But I've got many errors, saying "An object reference is required for non-static field, method or property". Is there any efficient way to do this with Regex? Thanks.

When you prefix the string with the "at" sign (@) you need to escape double quotes as "", not \". — Ed Gibbs
– Ed Gibbs, Commented Nov 11, 2014 at 14:41
Regex.Replace is a static method, he's using it fine. Though he' not using the return value in his example. — Jonesopolis
– Jonesopolis, Commented Nov 11, 2014 at 14:45

anubhava · Accepted Answer · 2014-11-11 14:53:47Z

1

Instead of (\w+?) in your regex you need to use:

([\w ]+)

To match words separated by space.

Or better you can use negation:

([^"]+)

Which means match 1 or more characters of anything but a double quote.

Your code would be:

Regex.Replace(inputString, 
      @"(?<=TextBlock Text="")([^""]+)(?="")", "Any given string comes here");

edited Nov 11, 2014 at 14:53

answered Nov 11, 2014 at 14:39

anubhava

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2 Comments

E_learner Over a year ago

I also tried your method, but with some change as dasblinkenlight and Ed Gibbs mentioned. I need to escape the double quotes with ", then your code works fine. Thanks.

anubhava Over a year ago

Ah ok I fixed escaping but I believe regex part was correct in my answer.

Sergey Kalinichenko · Accepted Answer · 2014-11-11 14:42:31Z

1

It looks like the problem is that you are trying to escape double-quotes inside your verbatim strings. This is not how it is done: you need to double your double-quotes inside such strings, like this:

@"(?<=TextBlock Text="")(\w+?)(?="")"

When you try escaping a double-quote with a slash, the parser gets confused, because it treats the double-quote as the end of the string. The characters after it produce syntax errors.

Note: with this error out of the way, consider fixing the catastrophic backtracking issue in your regex pattern.

answered Nov 11, 2014 at 14:42

Sergey Kalinichenko

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Comments

hwnd · Accepted Answer · 2014-11-11 15:00:22Z

1

You have three problems that cause this to not work as expected.

You are not assigning your replacement to anything.
You need to double your double quotes inside of your pattern instead of escaping them.
You need to account for whitespace between the words.

String result = Regex.Replace(inputString, @"(?<=TextBlock Text="")[\w\s]+(?="")", "Any given string comes here");

Ideone Demo

edited Nov 11, 2014 at 15:00

answered Nov 11, 2014 at 14:52

hwnd

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