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Using regular expression on string for use in C#

I'm trying to extract a url from a string.
{ns:"images",k:"5127",mid:"A04F21EB77CF61E10E43BA33CF1986CA44357448"
,md5:"e2987d19c953bd836ec8fd2e0aa8492",surl:"http://someURLIdontwant/"
,imgurl:"http://THISISTHEURLINEED.jpg",tid:"OIP.Me2987d199c953bd836ec8fd2e0aa8492H0"
,ow:"300", docid:"608010036892077154",oh:"225",tft:"49"}
So it is located after "imgurl:". I am no expert on Regex and all I could produce is:
imgurl:'(.*)',tid
whitch worked on some online regex tester. But not the way I'm using it in C# apperantly.
webClient.DownloadFile(System.Text.RegularExpressions.Regex.Match
(stringWithText, "imgurl:'(.*)',tid").Groups[1].Value,"path\file.jpg");
Can it be done? Thanks

As #WiktorStribiżew already pointed out: The expression is almost correct. Use this instead:
Regex.Match(stringWithText, "imgurl:\"(.*)\",tid").Groups[1].Value
Example on dotNetFiddle
And as I mentioned earlier in a comment: You should parse the Json data instead.

Regex Regular expression in c#

We have implemented the invocation of brill tagger from our c# code. We just neede to know what is the correct Regex regular expression for eliminating all from a string, but jst keep a-z,A-Z, full stop and comma. We tried [^a-zA-Z\.\,] on the online regular expression tester and it is giving the correct result, but when implemented in C#, it is not working properly. We also tried several other combinations but we are not getting the correct result.
This is the format in which we are writing:
strFileContent = Regex.Replace(strFileContent, #"[^a-zA-Z\.\,]", "");
but we are not getting the desired output. what is wrong??

Regex.Replace(yourString, #"[^a-z\.\,]", string.Empty, RegexOptions.IgnoreCase)
EDIT: I can't see anything wrong with what you are doing, my answer is exactly the same. I tested both in LINQPad and they both return the same result.

Can I add a regular expression into a .Net Assertion?

I'm trying to pull out page source from a set of pages and run an assertion on the results, this is a Test that runs to check that we are crawling specific pages in our site. Sometimes the results come back with a different case for the URL string, I'd like to account for that in the Assertion where I am checking page source. This is probably the wrong way to do this but I was wondering if there is a way to add in the .Net regex commands to the Assertion text. I have this as an assertion:
Assert.IsTrue(driver.PageSource.Contains("/explore"));
But is there a way to be sure that I can capture explore, Explore or EXPLORE? I though I could use (?i) here but that doesn't seem to work. I'm more used to Perl and it's regex capabilities but with C# and .Net I'm a little lost on where I can and can't use the inline regex commands.

Anthonys answer is valid, you don't really need regex. But if you do want to use it, you can use
Regex.IsMatch(driver.PageSource, "/explore", RegexOptions.IgnoreCase)

You don't need a regular expression to perform a case-insensitive check. Use IndexOf and compare that the result is greater than -1. IndexOf has overloads that allow you to specify if casing matters. Something like
bool containsExplore = driver.PageSource.IndexOf("/explore", StringComparison.InvariantCultureIgnoreCase) > -1;
Assert.IsTrue(containsExplore);

Try:
RegEx.Match("string", "regexp", RegExOptions.IgnoreCase).Success

How about using
StringAssert.Matches(string, regex);
In your case, that would translate to
StringAssert.Matches("drive.PageSource", "\/explore");

Does a .NET function exist that lets you pass in a string containing Regular Expressions and then return the possible matches?

Before I look into doing this myself, is there already a function out there that will do this:
I want to pass in a string containing text and RegEx markup and then it returns all possible matches it would look for in a string.
so the following passed to the method
abc|def|xyz
Would return 3 strings in an array or collection:
abc
def
xyz
Because that regex notation says to look for either abc, def or xyz.
I don't want this to search for the term in another string or anything like that, just return the possible matches it could make.
That's a simple example, anything that will do this for me, or shall I start writing the method myself?

With a simple regex as per your example it will work, but as soon as you start dealing with wild cards and repetition, it will have to generate almost an infinite amount of possible solutions, which in some cases may never even terminate.

No, it does not :)

RegEx replace with calculations?

Is it possible somehow to do a RegEx-replace with a calculation in the result? (in VS2010)
Such as:
Grid\.Row\=\"{[0-9]+}\"
to
Grid.Row="eval(int(\1) + 1)"

You can use a MatchEvaluator do achieve this, like
String s = Regex.Replace("1239", #"\d", m => (Int32.Parse(m.ToString()) + 1).ToString());
Output: 23410
Edit:
I just noticed... if you mean "using the VS2010 find-replace feature" and not "using C#", then the answer is "no", i am afraid.

You could always use capturing to retrieve any values you need for your calculation and then perform a RegEx Replace with a new RegEx that's constructed from you're equation and any values you captured.
If the equation doesn't use anything from the input text, one RegEx would be sufficient. You'd simply construct it by concatenating the static portions together with the computed value(s).

Unfortunately, C# and .NET do not provide an eval method or equivalent. However, it is possible to either use a library for expression parsing (a quick google gave me this .NET Math Expression Parser) or write your own (which is actually pretty easy, check out the Shunting-yard Algorithm and Postfix Notation). Simply capture the group then output the group value to the library/method you have written.
Edit: I see now you want this for the VS2010 program. This is unachievable unless you write your own VS extension. You could always write a program to search and replace your code and feed the code into it, then replace it the original code with its output.