• 增删改查注意事项


    1.查询

    context.Response.ContentType = "text/html";
    StringBuilder sb = new StringBuilder(); 注:定义一个长度可变的字符串
    sb.Append(@"</head> 
    <body>
    <a href='increase.html'>添加</a>
    <table width='600' border='1' cellspacing='0'>
    <tr>
    <td>学号</td>
    <td>姓名</td>
    <td>性别</td>
    <td>年龄</td>
    <td>操作</td>
    </tr>");
    string sql = "select * from student"; 注:查询的表
    SqlDataReader sqls = SQLHelper.ExecuteReader(sql); 注:查询的表变成一种一次读取一行的只进流
    while(sqls.Read())
    {
    sb.AppendFormat(@"<tr><td>{0}</td><td>{1}</td><td>{2}</td><td>{3}</td><td><a href='delete.ashx?id={4}' onclick='return confirm(&quot您确定要删除吗?&quot)'>删除</a>&nbsp;<a href='amend.ashx?id={5}' onclick='return confirm(&quot您确定要修改吗?&quot)'>修改</a></td></tr>", sqls["number"], sqls["name"], sqls["sex"], sqls["age"], sqls["number"], sqls["number"]); 注:url?id={5}传输数距,语法是键值对 键1=值1&键2=值2  &quot HTML转义符先当与  “ 。
    }
    sb.Append(@"</table></body></html>");
    context.Response.Write(sb.ToString()); 注:输出字符串(可变的)。。

    2.添加

    context.Response.ContentType = "text/html";
    string name = context.Request["nam"]; 注:获取name属性为nam
    string sex = context.Request["sex"]; 注:获取name属性为sex
    string age = context.Request["age"]; 注:获取name属性为age
    if (name == "" && sex == null && age == "")  注:判断获得的值是否为空
    {
    context.Response.Redirect("increase.html"); 注:跳转
    }
    else
    {
    string sql = "insert into Student(name,sex,age) values(@name,@sex,@age)";
    SqlParameter[] sp =
    {
    new SqlParameter("@name",name),
    new SqlParameter("@sex",sex),
    new SqlParameter("@age",age)
    };
    int i = SQLHelper.ExecuteNonQuery(sql, sp); 注:插入数距
    if (i == 1) 注:判断数距是否插入成功
    {
    context.Response.Redirect("Crud.ashx");
    }
    }

    3.删除

    context.Response.ContentType = "text/plain";
    string delete = context.Request["id"]; 注:获得传过来的id

    if (delete != null) 注:判断id是否为null
    {
    string sql = "delete Student where number=" + delete; 注:根据id删除
    SQLHelper.ExecuteNonQuery(sql);
    context.Response.Redirect("Crud.ashx"); 注:跳转
    }

    4.修改

    context.Response.ContentType = "text/html";
    string id = context.Request["id"]; 注:获得传过来的id
    if (id != null) 注:判断id是否为null,如果不为null
    {
    string sql = "select * from Student where number=" + id; 注:根据id查询
    DataTable dt = SQLHelper.ExecuteDataTable(sql);
    string str = File.ReadAllText(context.Request.MapPath("amend.html")); 注:根据相对路径获得绝对路径
    str = str.Replace("{number}", dt.Rows[0]["number"].ToString()); 注:将{number}占位符替换成dt.Rows[0]["number"]
    str = str.Replace("{nam}", dt.Rows[0]["name"].ToString()); 注:将{nam}占位符替换成dt.Rows[0]["name"]
    str = str.Replace("{age}", dt.Rows[0]["age"].ToString()); 注:将{age}占位符替换成dt.Rows[0]["age"]
    context.Response.Write(str); 注:输出str
    }
    else 注:如果为空
    {
    string number = context.Request["number"]; 注:获取name属性为number
    string name = context.Request["nam"]; 注:获取name属性为nam
    string sex = context.Request["sex"]; 注:获取name属性为sex
    string age = context.Request["age"]; 注:获取name属性为age
    if (number == "" && name == "" && sex == null && age == "") 注:判断值是否为空,如果为空
    {
    context.Response.Redirect("amend.html"); 注:跳转
    }
    else 注:如果不为空
    {
    string sql = "update Student set name=@name,sex=@sex,age=@age where number=" + number; 注:根据number修改
    SqlParameter[] sp =
    {
    new SqlParameter("@name",name),
    new SqlParameter("@sex",sex),
    new SqlParameter("@age",age)
    };
    int i = SQLHelper.ExecuteNonQuery(sql, sp);
    if (i == 1) 注:判断是否修改成功
    {
    context.Response.Redirect("Crud.ashx");
    }
    }
    }

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  • 原文地址:https://www.cnblogs.com/zhang1999/p/7210238.html
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