Question

I have a File, which contains text. Now, I have to replace some string with another. For Example I have to replace

"[ContactLetterSalutation]" 

with

 "Dear Thomas Kehl". 

Now, it is possible, that the placeholder "[ContactLetterSalutation]" contains somewhere "=\r\n" – this could be one, two or more times – for example

"[Conta=\r\ntLetterSa=\r\nlutation]".

I am searching now a way, that I can also replace this – I don’t know where and how many times there will be "=\r\n". The difficult is, that I should not replace all occurrences of "=\r\n" in the text. Can someone help me how to do this? Is there perhaps a possibility to do this with RegEx?

Thank you.
Best Regards, Thomas

Answer 1

string GetReplacement(Match m) {
    // Get the matched string.
    string x = m.ToString().Replace("=\r\n","");
    return Lookup[x];
}

...
file = Regex.Replace(file, @"\[.*?\]", GetReplacement, RegexOptions.Singleline);

edit:

RegexOptions.Singleline causes . to match \n

edit2:

While the above should work for small files, I think this question is more interesting for streams where you couldn’t get the whole file into a single string. I’ve come up with this but it probably has bugs:

static IEnumerable<string> Chunk(TextReader reader) {
    char[] chars = new char[MaxBufferSize];
    string buffer = "";
    int charsRead;
    while ((charsRead = reader.ReadBlock(chars, 0, MaxBufferSize)) > 0) {
        buffer = buffer + new string(chars,0,charsRead);
        int indexOfOpenBracket;
        if((indexOfOpenBracket = buffer.IndexOf('[')) == -1) {
            if (!string.IsNullOrEmpty(buffer)) yield return buffer;
            buffer = "";
            continue;
        }
        while (indexOfOpenBracket!=-1) {
            string outsideBrackets = buffer.Substring(0, indexOfOpenBracket);
            if(!string.IsNullOrEmpty(outsideBrackets)) yield return outsideBrackets;
            buffer = buffer.Substring(indexOfOpenBracket + 1);
            int indexOfCloseBracket = buffer.IndexOf(']');
            if (indexOfCloseBracket != -1) {
                string insideBrackets = buffer.Substring(0, indexOfCloseBracket);
                buffer = buffer.Substring(indexOfCloseBracket + 1);
                yield return DoLookup(insideBrackets);
            } else {
                buffer = '[' + buffer;
                break;
            }
            indexOfOpenBracket = buffer.IndexOf('[');
        }
    }
    yield return buffer;
}
public static void BufferReplace(Stream input, Stream output) {
    StreamReader reader = new StreamReader(input);
    StreamWriter writer = new StreamWriter(output);
    foreach (var chunk in Chunk(reader)) {
        writer.Write(chunk);
    }
    writer.Flush();
}