如何替换ac＃字符串中的特定字符？

Question

if I have a string along the lines of: "user:jim;id:23;group:49st;" how can I replace the group code (49st) with something else, so that it shows: "user:jim;id=23;group:76pm;"

sorry if the question is easy but I haven't found a specific answer, just cases different than mine.

Answer 1

You can use the index of "group" like this

string s = "user:jim;id:23;group:49st;";
string newS = s.Substring(0,s.IndexOf("group:") + 6);
string restOfS = s.IndexOf(";",s.IndexOf("group:") + 6) + 1 == s.Length 
? "" 
: s.Substring(s.IndexOf(";",s.IndexOf("group:") + 6) + 1);
newS += "76pm;";
s = newS + restOfS;

The line with the s = criteria ? true : false s = criteria ? true : false is essentially an if but it is put onto one line using a ternary operator.

Alternatively, if you know what text is there already and what it should be replaced with, you can just use a Replace

s = s.Replace("49st","76pm");

As an added precaution, if you are not always going to have this "group:" part in the string, to avoid errors put this inside an if which checks first

if(s.Contains("group:"))
{
    //Code
}

Answer 2

Find the match using regex and replace it with new value in original string as mentioned below:

string str = "user:jim;id=23;group:49st;";
var match = Regex.Match(str, "group:.*;").ToString();
var newGroup = "group:76pm;";
str = str.Replace(match, newGroup);

Answer 3

This solution should work no matter where the group appears in the string:

string input = "user:jim;id:23;group:49st;"; 
string newGroup = "76pm";
string output = Regex.Replace(input, "(group:)([^;]*)", "${1}"+newGroup);

Answer 4

Here is a very generic method for splitting your input, changing items, then rejoining items to a string. It is not meant for single replacement in your example, but is meant to show how to split and join items in string.

I used Regex to split the items and then put results into a dictionary.

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



namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string pattern = "(?'name'[^:]):(?'value'.*)";
            string input = "user:jim;id:23;group:49st";
            Dictionary<string,string> dict = input.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries).Select(x => new
            {
                name = Regex.Match(x, pattern).Groups["name"].Value,
                value = Regex.Match(x, pattern).Groups["value"].Value
            }).GroupBy(x => x.name, y => y.value)
            .ToDictionary(x => x.Key, y => y.FirstOrDefault());

            dict["group"] = "76pm";

            string output = string.Join(";",dict.AsEnumerable().Select(x => string.Join(":", new string[] {x.Key, x.Value})).ToArray());

        }
    }
}

Answer 5

That is just one way to do it. I hope it will help you.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace stringi
{
    class Program
    {
        static void Main(string[] args)
        {
            //this is your original string
            string s = "user:jim;id:23;group:49st";
            //string with replace characters
            string s2 = "76pm";

            //convert string to char array so you can rewrite character
            char[] c = s.ToCharArray(0, s.Length);

            //asign characters to right place
            c[21] = s2[0];
            c[22] = s2[1];
            c[23] = s2[2];
            c[24] = s2[3];

            //this is your new string
            string new_s = new string(c);

            //output your new string
            Console.WriteLine(new_s);

            Console.ReadLine();
        }
    }
}

Answer 6

string a = "user:jim;id:23;group:49st";

string b = a.Replace("49st", "76pm");

Console.Write(b);