using System.Collections.Specialized; //StringDictionary -> 键值集合, Key 不区分大小写..

string[] temp;

string a = "wang=asdf; li=yuio; zhao=qwewteqyrqyreqq; qian=dsahjdglsdagdjsalg";

string b = "zhou=dsagdsagsdahag; wang=xxxxxxxxxxyyyyyyyyyyzzzzzzzzzz; qian=ghjk; wu=saghdsaklg";

StringDictionary bs = new StringDictionary();

foreach (string var in b.Split(';'))
{
    temp = var.Split('=');
    temp[0] = temp[0].Trim();
    bs.Add(temp[0], temp[1]);
}

StringDictionary as = new StringDictionary();

foreach (string var in a.Split(';'))
{
    temp = var.Split('=');
    temp[0] = temp[0].Trim();
    if (bs.Contains(temp[0])) //bs.ContainsKey(temp[0])
    {
        as.Add(temp[0], bs[temp[0]]);
    }
    else
    {
        as.Add(temp[0], temp[1]);
    }
}

string result = "";

foreach (string var in a.Split(';'))
{
    temp = var.Split('=');
    
    if (bs.Contains(temp[0].Trim())) //bs.ContainsKey(temp[0].Trim())
    {
        result += temp[0] + "=" + bs[temp[0].Trim()];
    }
    else
    {
        result += temp[0] + "=" + temp[1];
    }
    
    result += ";";
}

Console.WriteLine(result);

            string a = "wang=asdf; li=yuio; zhao=qwewteqyrqyreqq; qian=dsahjdglsdagdjsalg";
            string b = "zhou=dsagdsagsdahag; wang=xxxxxxxxxxyyyyyyyyyyzzzzzzzzzz; qian=ghjk; wu=saghdsaklg";
            string[] aArray = a.Split(new char[] { '=', ';' }, StringSplitOptions.None);
            string[] bArray = b.Split(new char[] { '=', ';' }, StringSplitOptions.None);
            StringDictionary dic = new StringDictionary();
            for (int i = 0; i < aArray.Length-1; i+=2)
            {
                dic[aArray[i]] = aArray[i + 1];
            }
            for (int i = 0; i < bArray.Length - 1; i += 2)
            {
                dic[bArray[i]] = bArray[i + 1];
            }
            StringBuilder sb = new StringBuilder();
            foreach (string key in dic.Keys)
            { 
                sb.Append(key +"=" +dic[key] +";");
            }
            Console.WriteLine(sb.ToString());

Console.WriteLine(result.Substring(0, result.Length - 1)); //这样就可去除最后的";"

string a = "wang=asdf; li=yuio; zhao=qwewteqyrqyreqq; qian=dsahjdglsdagdjsalg";
            string b = "zhou=dsagdsagsdahag; wang=xxxxxxxxxxyyyyyyyyyyzzzzzzzzzz; qian=ghjk; wu=saghdsaklg";
            StringBuilder sb = new StringBuilder();
            Regex reg = new Regex(@"([^=]+?=)([^;]*?);\s*");

            foreach(Match m in reg.Matches(a + ";" + b + ";"))
            {
                Regex regM = new Regex(m.Groups[1].Value + @"([^;]*?);\s*");
                if (regM.IsMatch(sb.ToString()))
                {
                    sb.Replace(m.Groups[1].Value + regM.Match(sb.ToString()).Groups[1].Value ,m.Groups[1].Value + m.Groups[2].Value);
                }
                else
                    sb.Append("; " + m.Groups[1].Value + m.Groups[2].Value);
            }
            sb.Remove(0, 2);
            System.Diagnostics.Debug.WriteLine(sb.ToString());