c# Regex replace bracket pattern

Question

Hoping this would be an easy one for regex experts out there.

I have a text file that looks like this:

blah blah blah
[Image "pasted.bmp-20160720140433"]
blah blah
[Image "pasted.bmp-20160720140458"]
blah blah
[Image "download"]
blah blah
blah blah [Image "download3"] [Image "download5"] blah blah

I wish to replace the [Image "pasted.bmp-20160720140433"] with base64 embedded images. The image placements always start with "[Image " and always end with "]" the enclosing bracket.

Is there an easy regex replace that can do the job?

edit:

Ultimately I would like the string to be html compliant like this:

blah blah blah
<img src='data:image/png;base64,data_which_I_get_from_using_the_file_name' />
blah blah blah

Thank you very much.

Answer 1

\\[Image "([.\\-\\w]+)"\\] will match your pattern

A little explanation:

\\[Image " matches the first part of your pattern. The [ is escaped here as [] 's have special meaning in the Regex language
[.\\-\\w] is a list of characters - . matches a period, and \\- a hyphen. \\w matches any word character, which is AZ, az, or 0-9
The + means to match as many times in a row as possible
The () 's around [.\\-\\w]+ make it a capturing group, which means when a match is found, the image name will be made available.
Finally, "\\] matches the end of your pattern.

Note that when using this in C# you will need to escape certain characters to get the right string such as "\\\\[Image \\"([.\\\\-\\\\w]+)\\"]" or using an @-quoted string like @"\\[Image ""([.\\-\\w]+)""\\]"

Also, in the future, there are websites that can help with generating Regular Expressions and breaking down how they work, try inputting the above into regex101

---

Now, using Regex.Replace directly won't work, as I assume the base64 content will depend on the image name. In this case, you can use the Match class

An incomplete example might look like this:

string pattern = @"\[Image ""([.\-\w]+)""\]";
Regex rgx = new Regex(pattern);
string file = "...";

foreach (Match match in rgx.Matches(file))
{
    // Modify file here
    // match.Index will have the position of a match
    // match.Value will have the capture, e.g. "download3"
}