C#用ComboBox控件实现省与市的联动效果的方法

本文实例讲述了c#用combobox控件实现省与市的联动效果的方法。分享给大家供大家参考。具体实现方法如下：

using system; 
using system.collections.generic; 
using system.componentmodel; 
using system.data; 
using system.drawing; 
using system.linq; 
using system.text; 
using system.windows.forms; 
using system.data.sqlclient; 
using system.configuration; 
 
namespace 省市联动 
{ 
    public partial class form1 : form 
    { 
        public form1() 
        { 
            initializecomponent(); 
        } 
 
        private void form1_load(object sender, eventargs e) 
        { 
            tsql.getconnection(); 
            using (sqlconnection conn = new sqlconnection(tsql.getconnection())) 
            { 
                conn.open(); 
                using (sqlcommand cmd = conn.createcommand()) 
                { 
                    cmd.commandtext = "select * from promary"; 
                    using (sqldatareader dr = cmd.executereader()) 
                    { 
                        while (dr.read()) 
                        { 
                            province pr = new province(); 
                            pr.proid = dr.getint32(dr.getordinal("proid"));  //这里要特别注意数据库字段的类型 proid在数据库里是int型 
                            pr.proname = dr.getstring(dr.getordinal("proname")); 
                            combobox1.items.add(pr);//pr是一个province对象。province有一个proname和proid属性。我将一个对象填充到combobox1里。再让combobox1的displaymember属性设置proname。【也就是让combobox1显示pr对象的proname属性】。这样在填充市级城市的时候我就可以找到当前选择项combobox1.selecteditem（或者当前选择对象）所对应的proid 
                        } 
                    } 
                } 
                combobox1.selectedindex = 0;  //将comcombobox1的默认选项设为0 
            } 
        } 
 
        private void combobox2_selectedindexchanged(object sender, eventargs e) 
        { 
        } 
 
        private void combobox1_selectedindexchanged(object sender, eventargs e) 
        { 
            combobox2.items.clear(); //在选择的时候先清空一下combox1里面的所以项，以免在更换省名的时候，与先前对应的省名下的市没有删除。 
            province tem = (province)combobox1.selecteditem; // 因为在combobox1.items.add(pr)里添加的是对象。所以在这里讲combox1所选中的当前对象赋给tem对象 （tem对象下面有两个属性 proname和proid） 
             
            int id = tem.proid;  //将当前选中对象的的proid赋值给id，给下面的sql查询语句使用 
            tsql.getconnection();// 获取数据库连接字符串。 
            using (sqlconnection conn = new sqlconnection(tsql.getconnection())) 
            { 
                conn.open(); 
                using (sqlcommand cmd = conn.createcommand()) 
                { 
                     
                    cmd.commandtext = "select * from city where proid=@id"; 
                    cmd.parameters.add(new sqlparameter("id", id)); 
                    using (sqldatareader dr = cmd.executereader()) 
                    { 
                        while (dr.read()) 
                        { 
                            combobox2.items.add(dr.getstring(dr.getordinal("cityname"))); 
                        } 
                    } 
                } 
                combobox2.selectedindex = 0; //将comcombobox1的默认选项设为0 
            } 
        } 
    } 
    class tsql 
    { 
        public static string getconnection() //数据库连接字符串 
        { 
            string getconn = configurationmanager.connectionstrings["getconn"].connectionstring; 
            return getconn; 
        }        
    } 
    class province 
    { 
        public string proname { get; set; } 
        public int proid { get; set; } 
    } 
}

using system.data.sqlclient;
namespace 省市选择2
{
    public partial class form1 : form
    {
        publicform1()
        {
            initializecomponent();
        }
        privatevoid form1_load(objectsender,eventargs e)
        {
            /*
            //测试代码：执行这段代码的情况下是可以吧 tom这个值添加到 combobox1中的。
            people p1 = new people();
            p1.name = "tom";
            p1.age = 25;
            combobox1.items.add(p1.name);
            */
            using(sqlconnection conn =newsqlconnection("data source=凡斌-vaio;initialcatalog=dbpromary;integrated security=true"))
            {
                conn.open();
                using(sqlcommand cmd = conn.createcommand())
                {
                    cmd.commandtext = "select * from promary";
                    using(sqldatareader reader = cmd.executereader())
                    {
                        while (reader.read())
                        {
                            //string str =reader.getstring(reader.getordinal("proname"));
                            //combobox1.items.add(str);
                            province  pv =new  province();
                            //将combobox1控件的displaymember属性设置为“provincename”用来在combobox1控件中显示provincename属性的值
                           combobox1.displaymember = "provincename";
                            pv.provincename =reader.getstring(reader.getordinal("proname"));
                            pv.provinceid =reader.getint32(reader.getordinal("proid"));
                            //虽然pv属于对象，把一个对象添加到comboxbox1中，控件显示的值为对象的类名，但是在前面combobox1.displaymember ="provincename"处已经设置好控件要显示的为 province类的provincename值，所以添加进去的是pv对象的provincename值
                            combobox1.items.add(pv);
                        }                     
                    }
                }
            }
        }
 
        privatevoid combobox1_selectedindexchanged(object sender,eventargse)       //注意这里是combobox1不是combobox2
        {
            try
            {
                province  tem = (province) combobox1.selecteditem;
                int id = tem.provinceid;
 
                combobox2.items.clear();
                using(sqlconnection conn =newsqlconnection("data source=凡斌-vaio;initialcatalog=dbpromary;integrated security=true"))
                {
                    conn.open();
                    using (sqlcommand cmd = conn.createcommand())
                    {
                        //查询city（市）表里的 proid与promary（省）表里proid相同的所有数据。
                        cmd.commandtext = "select * from city where proid =@id";
                        cmd.parameters.add(new sqlparameter("id", id));
                        sqldatareader dr = cmd.executereader();
 
                        while(dr.read())
                        {
                           combobox2.items.add(dr.getstring(dr.getordinal("cityname")));
                        }
                    }
                }
            }
            catch(exception ex)
            {
                messagebox.show("错误信息：" + ex.message);
            }
        }
    }
  
    class province
    {
        public string provincename { get;set; }
        public int provinceid { get;set; }
    }
    //class people
    //{
    //   public string name { get; set; }
    //   public int age { get; set; }
    //}
}

如下图所示：

希望本文所述对大家的c#程序设计有所帮助。