StrinBuilder 追加 ,插入，删除，和替换操作

Stringbuilder.Append 提供了对Stringbuilder对象实例的结尾的追加指定类型的功能

Stringbuilder.AppendFormat 提供了对Stringbuilder对象实例的结尾的追加指定格式化字符类型的功能

StringBuilder sb = new StringBuilder();
                string str1 = ",";
                char[] char2 = { '>', '>', '>' };
                bool strbool = false;
                int i = 13;
                sb.Append(str1);
                sb.Append(char2);
                sb.Append(strbool);
                sb.Append(i);
                sb.AppendLine();
                sb.AppendFormat("字符串的值{0}", str1);
                sb.AppendFormat("字符数组值{0}", char2);
                sb.AppendLine();
                sb.AppendFormat("布尔值{0}", strbool);
                sb.AppendFormat("整型值{0:D}", i);
                Console.WriteLine(sb.ToString ());

学到这里后面对插入删除，替换基本都是和String是一样的只不过多建了一个Stringbuilder的对象；