如果key存在于使用linq的字典中，则向value添加额外的字符

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        Dictionary<string, string> dict = new Dictionary<string, string>()
        {
            { "key1", "value1" },
            { "key2", "value2" },
            { "key3", "value3" }
        };
        
        string key = "key2";
        string extraChar = "*";
        
        if (dict.ContainsKey(key))
        {
            dict = dict
                .Where(kvp => kvp.Key == key)
                .Select(kvp => new KeyValuePair<string, string>(kvp.Key, kvp.Value + extraChar))
                .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
        }
        
        foreach (var kvp in dict)
        {
            Console.WriteLine($"Key: {kvp.Key}, Value: {kvp.Value}");
        }
    }
}

Key: key1, Value: value1
Key: key2, Value: value2*
Key: key3, Value: value3