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  • 使用ADO.NET查询和操作数据2

    StringBuilder类: 用来定义可变字符串
    StringBuilder sb = new StringBuilder("");
    //追加字符串
    sb.Append("World");
    sb.Append("!");
    //W2orld
    sb.Insert(2, "2");
    //原字符串:Wo2rld! 截取之后:W2rld!
    sb.Remove(1, 2);
    //ToString()
    Console.WriteLine(sb.ToString());

    查询学生记录数
    //打开数据库连接
    con.Open();
    //使用StringBuilder追加SQL语句
    StringBuilder sb = new StringBuilder();
    sb.Append("select ");
    sb.Append(" Count(*) ");
    sb.Append(" from ");
    sb.Append("[Student]");
    Console.WriteLine(sb.ToString());
    //创建一个SqlCommand对象
    SqlCommand com = new SqlCommand(sb.ToString(),con);
    Console.WriteLine((int)com.ExecuteScalar());


    DataReader:从数据源中检索只读、只进的数据流,每次读取一行数据


    StringBuilder sb = new StringBuilder();
    sb.AppendLine("select");
    sb.AppendLine("[StudentNo]");
    sb.AppendLine(",[StudentName]");
    sb.AppendLine("from");
    sb.AppendLine("[Student]");
    SqlCommand com = new SqlCommand(sb.ToString(), con);
    //从数据源中检索只读、只进的数据流
    return com.ExecuteReader();


    SqlDataReader reader=GetStudentInfo();
    while (reader.Read())
    {
    Console.WriteLine("{0} {1}",reader["StudentNo"],reader["StudentName"]);
    }
    reader.Close();


    ExecuteNonQuery():

    StringBuilder sb = new StringBuilder();
    sb.AppendLine("Insert into");
    sb.AppendLine("[Grade]([GradeName])");
    sb.AppendLine("Values('" + gradeName + "')");
    //3.创建一个SqlCommand
    SqlCommand com = new SqlCommand(sb.ToString(),con);
    //4.返回执行结果
    return com.ExecuteNonQuery();


    Student stu = new Student();
    Console.WriteLine("请输入年级名称:");
    string gradename = Console.ReadLine();
    int count = stu.AddGrade(gradename);
    if (count > 0)
    {
    Console.WriteLine("success!");
    }
    else
    {
    Console.WriteLine("success mother!");
    }

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  • 原文地址:https://www.cnblogs.com/fkx1/p/7757703.html
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