一.使用StringBuilder类追加和删除字符串
1.创建StringBuilder类的对象
StringBuilder sb=new StringBuilder("初始字符串值");
2.Append()方法拼接字符串
sb.Append("呵呵");
结果为：初始字符串值呵呵
3.使用Insert()方法在指定位置插入字符串
sb.Insert(位置，字符串);
sb.Insert(2,"化");
结果为：初始化字符串值呵呵
4.使用Remove()方法删除字符串
sb.Remove(开始位置,删除长度)
sb.Remove(7,2);
结果为：初始化字符串值
二.DataRader对象读取数据
1.HasRows属性：判断是否读取到数据，如果有数据则为true，反之为false
2.Read()方法：前进到下一行读取的数据
3.Close()方法：关闭DataReader对象
案例：
StringBuilder sb = new StringBuilder();
???????????????//selectcount(*)fromStudent
???????????????sb.AppendLine("SELECT ");
???????????????sb.AppendLine(" [StudentNo] ");
???????????????sb.AppendLine(" ,[StudentName] ");
???????????????sb.AppendLine(" from ");
???????????????sb.AppendLine(" Student ");
???????????????SqlCommand com = new SqlCommand(sb.ToString(), con);
???????????????SqlDataReader dr=com.ExecuteReader();
???????????????//判断DataReader对象是否返回结果，如果有返回结果HasRows的值为true，则循环读取
???????????????if (dr.HasRows)
???????????????{
???????????????????while (dr.Read())
???????????????????{
???????????????????????Console.WriteLine("姓名：" + dr["StudentName"] + "\t学号：" + dr["StudentNo"]);
???????????????????}
???????????????}
???????????????//关闭DataReader对象
???????????????dr.Close();
???????三.使用Command对象的ExcuteNonQuery()方法操作数据
ExcuteNonQuery()主要用于对数据的增加修改以及删除
案例:添加年级信息
StringBuilder sb = new StringBuilder();
???????????????????sb.AppendLine("insert into ");
???????????????????sb.AppendLine(" Grade ");
???????????????????sb.AppendLine(" ([GradeName]) ");
???????????????????sb.AppendLine(" values ");
???????????????????sb.AppendLine(" (‘"+gradeName+"‘)");
???????????????????SqlCommand com = new SqlCommand(sb.ToString(),con);
???????????????????int count=com.ExecuteNonQuery();
使用ADO.NET查询和操作数据-----的解析
原文地址：https://www.cnblogs.com/bk1234/p/9389832.html