C#通过子窗体刷新父窗体的实现方法

public delegate void eventhandler(object sender,eventargs e)
参数说明
sender：事件源。
e：不包含任何事件数据的eventargs事件数据。

/// <summary>
/// 某一个事件，比如，添加
/// </summary>
private void button1_click(object? sender, eventargs e)
{
    globalflag = true;                          //设定标识的值为true
    if (!(combobox1.items.equals(idcontent)))   //当combobox控件中不存在将添加的信息时
    {
        combobox1.items.add(idcontent!);        //在combobox控件中添加一条记录
    }
    updatedata();
}
 
// 其它
 
/// <summary>
/// 更新datagridview控件中的内容
/// </summary>
protected void updatedata()
{
    updatedatagridview?.invoke(this, eventargs.empty);
}

// 添加子窗体的事件
public void createfrmchild()
{
    frm_child babywindow = new()
    {
        mdiparent = this,
    };
    datagridview1.controls.add(babywindow);
    babywindow.updatedatagridview += new eventhandler(babywindow_updatedatagridview!);
    babywindow.show();
}
 
// 其它
 
/// <summary>
/// 实现事件委托
/// </summary>
void babywindow_updatedatagridview(object sender, eventargs e)
{
    // 其它
}

//数据库连接字符串
readonly string? connstring = "data source=desktop-3lv13fs;database=db_tomeone;integrated security=sspi;trustservercertificate=true;";

namespace _197
{
    partial class frm_main
    {
        /// <summary>
        ///  required designer variable.
        /// </summary>
        private system.componentmodel.icontainer components = null;
 
        /// <summary>
        ///  clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.dispose();
            }
            base.dispose(disposing);
        }
 
        #region windows form designer generated code
 
        /// <summary>
        ///  required method for designer support - do not modify
        ///  the contents of this method with the code editor.
        /// </summary>
        private void initializecomponent()
        {
            menustrip1 = new menustrip();
            toolstripmenuitem1 = new toolstripmenuitem();
            toolstripmenuitem2 = new toolstripmenuitem();
            toolstripmenuitem3 = new toolstripmenuitem();
            datagridview1 = new datagridview();
            menustrip1.suspendlayout();
            ((system.componentmodel.isupportinitialize)datagridview1).begininit();
            suspendlayout();
            // 
            // menustrip1
            // 
            menustrip1.backcolor = systemcolors.controldark;
            menustrip1.items.addrange(new toolstripitem[] { toolstripmenuitem1 });
            menustrip1.location = new point(0, 0);
            menustrip1.name = "menustrip1";
            menustrip1.size = new size(335, 25);
            menustrip1.tabindex = 0;
            menustrip1.text = "menustrip1";
            // 
            // toolstripmenuitem1
            // 
            toolstripmenuitem1.dropdownitems.addrange(new toolstripitem[] { toolstripmenuitem2, toolstripmenuitem3 });
            toolstripmenuitem1.name = "toolstripmenuitem1";
            toolstripmenuitem1.size = new size(44, 21);
            toolstripmenuitem1.text = "操作";
            // 
            // toolstripmenuitem2
            // 
            toolstripmenuitem2.name = "toolstripmenuitem2";
            toolstripmenuitem2.size = new size(136, 22);
            toolstripmenuitem2.text = "添加或删除";
            toolstripmenuitem2.click += toolstripmenuitem2_click;
            // 
            // toolstripmenuitem3
            // 
            toolstripmenuitem3.name = "toolstripmenuitem3";
            toolstripmenuitem3.size = new size(136, 22);
            toolstripmenuitem3.text = "退出";
            toolstripmenuitem3.click += toolstripmenuitem3_click;
            // 
            // datagridview1
            // 
            datagridview1.allowusertoaddrows = false;
            datagridview1.columnheadersheightsizemode = datagridviewcolumnheadersheightsizemode.autosize;
            datagridview1.dock = dockstyle.fill;
            datagridview1.location = new point(0, 25);
            datagridview1.name = "datagridview1";
            datagridview1.size = new size(335, 178);
            datagridview1.tabindex = 1;
            // 
            // frm_main
            // 
            autoscaledimensions = new sizef(7f, 17f);
            autoscalemode = autoscalemode.font;
            clientsize = new size(335, 203);
            controls.add(datagridview1);
            controls.add(menustrip1);
            ismdicontainer = true;
            mainmenustrip = menustrip1;
            name = "frm_main";
            text = "主窗体";
            load += frm_main_load;
            menustrip1.resumelayout(false);
            menustrip1.performlayout();
            ((system.componentmodel.isupportinitialize)datagridview1).endinit();
            resumelayout(false);
            performlayout();
        }
 
        #endregion
 
        private menustrip menustrip1;
        private toolstripmenuitem toolstripmenuitem1;
        private toolstripmenuitem toolstripmenuitem2;
        private toolstripmenuitem toolstripmenuitem3;
        private datagridview datagridview1;
    }
}

// 通过子窗体刷新父窗体
// 设置主窗体的ismdicontainer=true;
using system.data;
using microsoft.data.sqlclient;
 
namespace _197
{
    public partial class frm_main : form
    {   
        public frm_main()
        {
            initializecomponent();
        }
 
        #region 声明的变量
        private static bool flag = false;   //标识是否创建新的子窗体
        readonly frm_child babywindow = new();//实例化一个子窗体
        readonly dataset pubsset = new();   //定义一个数据集对象
        private static string[]? idarray;   //声明一个一维字符串数组
        public datatable? idtable;          //声明一个数据表对象
        sqldataadapter? idadapter;          //声明一个数据读取器对象
        sqldataadapter? pubsadapter;        //声明一个数据读取器对象
        sqlconnection? connpubs;            //声明一个数据库连接对象
        sqlcommand? personalinformation;    //声明一个执行sql语句的对象
 
        public static string[]? idarray { get => idarray; set => idarray = value; }
        public static bool flag { get => flag; set => flag = value; }
        
        readonly string? connstring         //数据库连接字符串
            = "data source=desktop-3lv13fs;database=db_tomeone;integrated security=sspi;trustservercertificate=true;";
        #endregion
 
        private void frm_main_load(object? sender, eventargs e)
        {
            string adapterstring = "select userid as 编号,username as 姓名 ,phone as 电话,address as 住址 from tb_user";//用于查询的字符串
            string idstring = "select userid from tb_user";//读取数据库中用户的id编号字符串
            connpubs = new sqlconnection(connstring);//建立数据库连接
            pubsadapter = new sqldataadapter(adapterstring, connpubs);//创建pubsadapter数据读取器
            idadapter = new sqldataadapter(idstring, connpubs);       //用于读取用户编号的读取器
            pubsadapter.fill(pubsset, "tb_user");            //填充pubsset数据集
            idadapter.fill(pubsset, "id");                   //填充pubsset数据集
            datatable pubstable = pubsset.tables["tb_user"]!;//将数据写入pubstable表
            idtable = pubsset.tables["id"]!;                 //将数据写入id表
            idarray = new string[idtable.rows.count];        //为数组定义最大长度
            datagridview1.datasource = pubstable.defaultview;//设置datagridview1的数据源
            for (int i = 0; i < idtable.rows.count; i++)     //循环遍历数据表中的每一行数据
            {
                for (int j = 0; j < idtable.columns.count; j++)//循环遍历数据表中的每一列数据
                {
                    idarray[i] = idtable.rows[i][j].tostring()!;//将数据表中的数据添加至一个一维数组
                }
            }
        }
 
        #region 创建子窗体的createfrmchild方法
        /// <summary>
        /// 设置子窗体的父窗体为当前窗体;
        /// 实例化一个子窗体;
        /// 在datagridview控件中添加子窗体;
        /// 显示子窗体;
        /// </summary>
        public void createfrmchild()
        {
            frm_child babywindow = new()
            {
                mdiparent = this,
            };
            datagridview1.controls.add(babywindow);
            babywindow.updatedatagridview += new eventhandler(babywindow_updatedatagridview!);
            babywindow.show();
        }
        /// <summary>
        /// 事件委托
        /// </summary>
        void babywindow_updatedatagridview(object sender, eventargs e)
        {
            if (frm_child.globalflag == false)    //当单击删除按钮时
            {
                if (connpubs!.state == connectionstate.closed) //当数据库处于断开状态时
                {
                    connpubs.open();              //打开数据库的连接
                }
                string afreshstring = "delete tb_user where userid=" + frm_child.deleteid!.trim();//定义一个删除数据的字符串
                personalinformation = new sqlcommand(afreshstring, connpubs); //执行删除数据库字段
                personalinformation.executenonquery(); //执行sql语句并返回受影响的行数
                connpubs.close();                      //关闭数据库
                displaydata();                         //显示数据库更新后的内容
                messagebox.show("数据删除成功！", "提示信息", messageboxbuttons.ok, messageboxicon.asterisk);
            }
            else
            {
                if (connpubs!.state == connectionstate.closed) //当数据库处于关闭状态时
                {
                    connpubs.open();    //打开数据库
                }
                string insertstring = "insert into tb_user values('" + frm_child.idcontent + "','" + frm_child.namecontent + "','" + frm_child.phonecontent + "','" + frm_child.addresscontent + "')";//定义一个插入数据的字符串变量
                personalinformation = new sqlcommand(insertstring, connpubs);//执行插入数据库字段
                personalinformation.executenonquery();          //执行sql语句并返回受影响的行数
                connpubs.close();        //关闭数据库
                displaydata();           //显示更新后的数据
                messagebox.show("数据添加成功！", "提示信息", messageboxbuttons.ok, messageboxicon.asterisk);
            }
        }
        #endregion
 
        #region 用于读取数据库的displaydata方法
        public void displaydata()
        {
            pubsset.clear();
            connpubs = new sqlconnection(connstring); 
            string displaystring = "select userid as 编号,username as 姓名 ,phone as 电话,address as 住址 from tb_user";//定义读取数据库的字段
            sqldataadapter personaladapter = new(displaystring, connpubs);    //定义一个读取数据库数据的读取器
            personaladapter.fill(pubsset, "tb_user");                                            //向表displaytable中填充数据
            datagridview1.datasource = pubsset.tables["tb_user"]!.defaultview; //设定datagridview控件的数据源
        }
        #endregion
        /// <summary>
        /// 添加或删除记录
        /// 创建子窗体的createfrmchild方法
        /// </summary>
        private void toolstripmenuitem2_click(object sender, eventargs e)
        {
            if (flag == false)   //判断标识的值决定是否创建窗体
            {
                createfrmchild();//创建子窗体
            }
            for (int i = 0; i < datagridview1.controls.count; i++)                      //循环遍历datagridview控件上的控件集
            {
                if (datagridview1.controls[i].name.equals(babywindow.name)) //当存在子窗体时
                {
                    flag = true; //改变标识flag的值
                    break;       //退出循环体
                }
            }
        }
        /// <summary>
        /// 退出
        /// </summary>
        private void toolstripmenuitem3_click(object sender, eventargs e)
        {
            application.exit();
        }
    }
}

namespace _197
{
    partial class frm_child
    {
        /// <summary>
        /// required designer variable.
        /// </summary>
        private system.componentmodel.icontainer components = null;
 
        /// <summary>
        /// clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.dispose();
            }
            base.dispose(disposing);
        }
 
        #region windows form designer generated code
 
        /// <summary>
        /// required method for designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void initializecomponent()
        {
            groupbox1 = new groupbox();
            button2 = new button();
            button1 = new button();
            record_address = new textbox();
            record_phone = new textbox();
            record_name = new textbox();
            record_id = new textbox();
            label4 = new label();
            label3 = new label();
            label2 = new label();
            label1 = new label();
            groupbox2 = new groupbox();
            button3 = new button();
            combobox1 = new combobox();
            label5 = new label();
            groupbox1.suspendlayout();
            groupbox2.suspendlayout();
            suspendlayout();
            // 
            // groupbox1
            // 
            groupbox1.controls.add(button2);
            groupbox1.controls.add(button1);
            groupbox1.controls.add(record_address);
            groupbox1.controls.add(record_phone);
            groupbox1.controls.add(record_name);
            groupbox1.controls.add(record_id);
            groupbox1.controls.add(label4);
            groupbox1.controls.add(label3);
            groupbox1.controls.add(label2);
            groupbox1.controls.add(label1);
            groupbox1.location = new point(12, 12);
            groupbox1.name = "groupbox1";
            groupbox1.size = new size(270, 157);
            groupbox1.tabindex = 0;
            groupbox1.tabstop = false;
            groupbox1.text = "添加信息";
            // 
            // button2
            // 
            button2.location = new point(187, 56);
            button2.name = "button2";
            button2.size = new size(75, 23);
            button2.tabindex = 9;
            button2.text = "清空";
            button2.usevisualstylebackcolor = true;
            button2.click += button2_click;
            // 
            // button1
            // 
            button1.location = new point(187, 25);
            button1.name = "button1";
            button1.size = new size(77, 23);
            button1.tabindex = 8;
            button1.text = "提交";
            button1.usevisualstylebackcolor = true;
            button1.click += button1_click;
            // 
            // record_address
            // 
            record_address.location = new point(72, 118);
            record_address.name = "record_address";
            record_address.size = new size(100, 23);
            record_address.tabindex = 7;
            record_address.textchanged += record_address_textchanged;
            // 
            // record_phone
            // 
            record_phone.location = new point(72, 87);
            record_phone.name = "record_phone";
            record_phone.size = new size(100, 23);
            record_phone.tabindex = 6;
            record_phone.textchanged += record_phone_textchanged;
            // 
            // record_name
            // 
            record_name.location = new point(72, 56);
            record_name.name = "record_name";
            record_name.size = new size(100, 23);
            record_name.tabindex = 5;
            record_name.textchanged += record_name_textchanged;
            // 
            // record_id
            // 
            record_id.location = new point(72, 25);
            record_id.name = "record_id";
            record_id.size = new size(100, 23);
            record_id.tabindex = 4;
            record_id.textchanged += record_id_textchanged;
            // 
            // label4
            // 
            label4.autosize = true;
            label4.location = new point(11, 118);
            label4.name = "label4";
            label4.size = new size(44, 17);
            label4.tabindex = 3;
            label4.text = "地址：";
            // 
            // label3
            // 
            label3.autosize = true;
            label3.location = new point(11, 87);
            label3.name = "label3";
            label3.size = new size(44, 17);
            label3.tabindex = 2;
            label3.text = "电话：";
            // 
            // label2
            // 
            label2.autosize = true;
            label2.location = new point(11, 56);
            label2.name = "label2";
            label2.size = new size(44, 17);
            label2.tabindex = 1;
            label2.text = "姓名：";
            // 
            // label1
            // 
            label1.autosize = true;
            label1.location = new point(11, 25);
            label1.name = "label1";
            label1.size = new size(44, 17);
            label1.tabindex = 0;
            label1.text = "编号：";
            // 
            // groupbox2
            // 
            groupbox2.controls.add(button3);
            groupbox2.controls.add(combobox1);
            groupbox2.controls.add(label5);
            groupbox2.location = new point(12, 175);
            groupbox2.name = "groupbox2";
            groupbox2.size = new size(270, 54);
            groupbox2.tabindex = 1;
            groupbox2.tabstop = false;
            groupbox2.text = "删除信息";
            // 
            // button3
            // 
            button3.location = new point(187, 24);
            button3.name = "button3";
            button3.size = new size(75, 23);
            button3.tabindex = 2;
            button3.text = "删除";
            button3.usevisualstylebackcolor = true;
            button3.click += button3_click;
            // 
            // combobox1
            // 
            combobox1.formattingenabled = true;
            combobox1.location = new point(72, 24);
            combobox1.name = "combobox1";
            combobox1.size = new size(100, 25);
            combobox1.tabindex = 1;
            // 
            // label5
            // 
            label5.autosize = true;
            label5.location = new point(11, 30);
            label5.name = "label5";
            label5.size = new size(44, 17);
            label5.tabindex = 0;
            label5.text = "编号：";
            // 
            // frm_child
            // 
            autoscaledimensions = new sizef(7f, 17f);
            autoscalemode = autoscalemode.font;
            clientsize = new size(294, 241);
            controls.add(groupbox2);
            controls.add(groupbox1);
            maximizebox = false;    //最大化按钮没有意义
            name = "frm_child";
            startposition = formstartposition.centerscreen;
            text = "子窗体";
            formclosing += frm_child_formclosing;
            load += frm_child_load;
            groupbox1.resumelayout(false);
            groupbox1.performlayout();
            groupbox2.resumelayout(false);
            groupbox2.performlayout();
            resumelayout(false);
        }
 
        #endregion
 
        private groupbox groupbox1;
        private textbox record_address;
        private textbox record_phone;
        private textbox record_name;
        private textbox record_id;
        private label label4;
        private label label3;
        private label label2;
        private label label1;
        private groupbox groupbox2;
        private button button2;
        private button button1;
        private button button3;
        private combobox combobox1;
        private label label5;
    }
}

// 本实例仅可创建一个窗口:
// 最大化后没有实际意义，因此关闭maximizebox属性值为false
namespace _197
{
    public partial class frm_child : form
    {
        #region 变量的声明
        public event eventhandler? updatedatagridview = null;//定义一个处理更新datagridview控件内容的方法
        private static string? deleteid;        //定义一个表示删除数据编号的字符串
        private static string? idcontent;       //该变量用来存储数据编号
        private static string? namecontent;     //该变量用来存储姓名
        private static string? phonecontent;    //该变量用来存储电话
        private static string? addresscontent;  //该变量用来存储住址
        private static bool globalflag;         //该变量用来标识是否创建新的子窗体
 
        public static string? deleteid { get => deleteid; set => deleteid = value; }
        public static string? idcontent { get => idcontent; set => idcontent = value; }
        public static string? namecontent { get => namecontent; set => namecontent = value; }
        public static string? phonecontent { get => phonecontent; set => phonecontent = value; }
        public static string? addresscontent { get => addresscontent; set => addresscontent = value; }
        public static bool globalflag { get => globalflag; set => globalflag = value; }
        #endregion
 
        public frm_child()
        {
            initializecomponent();
        }
        /// <summary>
        /// 添加
        /// </summary>
        private void button1_click(object? sender, eventargs e)
        {
            globalflag = true;                          //设定标识的值为true
            if (!(combobox1.items.equals(idcontent)))   //当combobox控件中不存在将添加的信息时
            {
                combobox1.items.add(idcontent!);        //在combobox控件中添加一条记录
            }
            updatedata();
        }
        /// <summary>
        /// 清空
        /// </summary>
        private void button2_click(object? sender, eventargs e)
        {
            record_id.clear();      //清空编号文本框中的内容
            record_name.clear();    //清空姓名文本框中的内容
            record_phone.clear();   //清空电话号码文本框中的内容
            record_address.clear(); //清空居住地址文本框中的内容
            record_id.focus();      //设定当前鼠标的焦点在编号文本框中
        }
        /// <summary>
        /// 删除
        /// </summary>
        private void button3_click(object? sender, eventargs e)
        {
            globalflag = false;             //设定全局变量表示为false
            if (combobox1.items.count > 1)  //当combobox中剩不小于2条内容时
            {
                deleteid = combobox1.selecteditem!.tostring();  //将选中项转化为int型
                if (combobox1.items.count != 0)                 //当combobox中剩1条内容时
                {
                    combobox1.items.remove(combobox1.selecteditem);
                    combobox1.selectedindex = 0;
                }
            }
            updatedata(); 
        }
        /// <summary>
        /// 保存新添加记录的编号
        /// </summary>
        private void record_id_textchanged(object? sender, eventargs e)
        {
            idcontent = record_id.text;
        }
        /// <summary>
        /// 保存填入的姓名
        /// </summary>
        private void record_name_textchanged(object? sender, eventargs e)
        {
            namecontent = record_name.text;
        }
        /// <summary>
        /// 保存填入的电话号码
        /// </summary>
        private void record_phone_textchanged(object? sender, eventargs e)
        {
            phonecontent = record_phone.text;
        }
        /// <summary>
        /// 保存填入的地址信息
        /// </summary>
        private void record_address_textchanged(object? sender, eventargs e)
        {
            addresscontent = record_address.text;
        }
        /// <summary>
        /// 循环遍历数组中的每一个元素,向combobox控件中添加内容
        /// 默认设定当前选中项的索引为0
        /// </summary>
        private void frm_child_load(object? sender, eventargs e)
        {
            for (int i = 0; i < frm_main.idarray!.length; i++)
            {
                combobox1.items.add(frm_main.idarray[i].tostring());
                combobox1.selectedindex = 0;
            }
        }
        /// <summary>
        /// 设定该值为false表示可以创建新窗体
        /// </summary>
        private void frm_child_formclosing(object? sender, formclosingeventargs e)
        {
            frm_main.flag = false; 
        }
       
        /// <summary>
        /// 更新datagridview控件中的内容
        /// </summary>
        protected void updatedata()
        {
            updatedatagridview?.invoke(this, eventargs.empty);
        }
    }
}