不知道合不合要求: 
public string A(string Name)
        {
            string value="",sConst;
            sConst="Server=198.198.1.16;Database=myDb;User Id=test;Password=1234567890";
            char[] c1 = new char[] { ';' };
            string[] ss = sConst.Split(c1);
            string[] sName=new string[ss.Length];
            string[] sValue = new string[ss.Length];
            int i = 0;
            foreach (string s in ss)
            {
                char[] c2 = new char[] { '=' };
                sName[i] = s.Split(c2)[0];
                sValue[i] = s.Split(c2)[1];
                if (sName[i].Equals(Name))
                {
                    value = sValue[i];
                }
                i++;            }
            return value;
        }