c# Replace text within curly brackets, including the curly brackets

Question

I'm trying to replace a string,enclosed in curly brackets.

If I use the Replace method provided by the Regex class and I don't specify the curly brackets, the string is found and replaced correctly, but if I do specify the curly brackets like this: {{FullName}} , the text is left untouched.

   var pattern = "{{" + keyValue.Key + "}}";
   docText = new Regex(pattern, RegexOptions.IgnoreCase).Replace(docText, keyValue.Value);

Take this string as a example

Dear {{FullName}}

I want to replace it with John , so that the text ends up like this:

Dear John .

How can I express the regex, so that the string is found and replace correctly?

Answer 1

You don't need a regular expression if the key is just a string. Just replace "{{FullName}}" with "John". example:

string template = "Dear {{FullName}}";
string result = template.Replace("{{" + keyValue.Key + "}}", keyValue.Value);

Edit: addressing concerns that this doesn't work...

The following is a complete example. You can run it at https://dotnetfiddle.net/wnIkvf

using System;
using System.Text.RegularExpressions;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        var keyValue = new KeyValuePair<string,string>("FullName", "John");
        string docText = "Dear {{FullName}}";
        string result = docText.Replace("{{" + keyValue.Key + "}}", keyValue.Value);
        Console.WriteLine(result);
    }
}

Answer 2

Looking for "Dear {{FullName}}" to "Dear John" ?

not a regex solution... but this is how I prefer to do it sometimes.

string s = "Dear {{FullName}}";
// use regex to replace FullName like you mentioned before, then...
s.Replace("{",string.empty);
s.Replace("}",string.empty);

Answer 3

var keyValue = new KeyValuePair<string,string>("FullName", "John");
var pattern = "{{" + keyValue.Key + "}}";
Console.WriteLine(new Regex(Regex.Escape(pattern), RegexOptions.IgnoreCase).Replace("Dear {{FullName}}", keyValue.Value));

Output:

Dear John

Answer 4

If you actually want to use a regular expression, then escape your literal text to turn it into a regular expression pattern using Regex.Escape .

var keyValue = new KeyValuePair<string,string>("FullName", "John");
string docText = "Dear {{FullName}}";
var pattern = "{{" + keyValue.Key + "}}";
docText = new Regex(Regex.Escape(pattern), RegexOptions.IgnoreCase).Replace(docText, keyValue.Value);

docText will be Dear John

Answer 5

What I believe is that you really want to do is replace multiple things in a document.

To do so use the regex pattern I provide, but also use the regex replace match evaluator delegate. What that does, is that every match can be actively evaluated for each item and a proper item will be replaced as per C# logic.

Here is an example with two possible keywords setup.

string text = "Dear {{FullName}}, I {{UserName}} am writing to say what a great answer!";

string pattern = @"\{\{(?<Keyword>[^}]+)\}\}";

var replacements 
   = new Dictionary<string, string>() { { "FullName", "OmegaMan" }, { "UserName", "eddy" } };

Regex.Replace(text, pattern, mt =>
{

    return replacements.ContainsKey(mt.Groups["Keyword"].Value)
           ? replacements[mt.Groups["Keyword"].Value]
           : "???";

}
);

Result

Dear OmegaMan, I eddy am writing to say what a great answer!

---

The preceding example uses

• Match Evaluator Delegate
• Named match capture groups (?<{Name here}> …)
• Set Negation [^ ] which says match until the negated item is found, in this case a closing curly } .