項(xiàng)目需求：根據(jù)年級(jí)下拉框的變化使得科目下拉框綁定次年級(jí)下對(duì)應(yīng)有的值
我們用三層架構(gòu)的模式來(lái)實(shí)現(xiàn)
1.我們想和數(shù)據(jù)庫(kù)交互，我們首先得來(lái)先解決dal數(shù)據(jù)庫(kù)交互層
01.獲得年級(jí)下拉框的數(shù)據(jù)
在gradedal類中
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using system;using system.collections.generic;using system.linq;using system.text;using system.threading.tasks;using system.data.sqlclient;using system.data;using myschool.model;using system.configuration;namespace myschool.dal{ //數(shù)據(jù)訪問(wèn)層 public class gradedal { public static string constr = configurationmanager.connectionstrings["constr"].connectionstring; #region 獲得年級(jí)表 public datatable selectgrade(string gradetype) { //和數(shù)據(jù)庫(kù)交互 string str = "data source=.;initial catalog=myschool;uid=sa"; sqlconnection con = new sqlconnection(str); string sql = ""; if (gradetype=="") { sql = "select * from grade"; } else { sql = "select * from student where gradeid in (select gradeid from grade where gradename='" + gradetype + "')"; } sqldataadapter da = new sqldataadapter(sql, con); dataset ds = new dataset(); //捕獲異常 try { da.fill(ds, "stuinfo"); } catch (exception ex) { throw new exception(ex.message); } //返回一張表的數(shù)據(jù) return ds.tables["stuinfo"]; } #endregion #region 獲取年級(jí)數(shù)據(jù)，為在下拉框中顯示 //定義一個(gè)集合,儲(chǔ)存年級(jí)信息 list<grade> list = new list<grade>(); #region 方法一: 以返回表的方式 public datatable loadcombox() { string sql = "select * from grade"; datatable dt = sqlhelper.executedatatable(sql); return dt; } #endregion #region 方法二:以返回集合的方式 public list<grade> loadcombox2() { string sql = "select * from grade"; datatable dt = sqlhelper.executedatatable(sql); //方法一： foreach (datarow row in dt.rows) { //每一個(gè)row代表表中的一行,所以一行對(duì)應(yīng)一個(gè)年級(jí)對(duì)象 grade grade = new grade(); grade.gradeid = convert.toint32(row["gradeid"]); grade.gradename = row["gradename"].tostring(); list.add(grade); } //方法二：(使用mytool類) //mytool tool=new mytool(); //list = tool.datatabletolist<grade>(dt); return list; } #endregion #region 方法三：要求使用using語(yǔ)句 public list<grade> loadcombox3() { //using的作用可以釋放資源，利于資源的回收（可以省略關(guān)閉連接） using (sqlconnection con=new sqlconnection(constr)) { try { string sql = "select * from grade"; sqlcommand cmd = new sqlcommand(sql,con); con.open(); sqldatareader dr = cmd.executereader(); while (dr.read()) { grade gr = new grade(); gr.gradeid = convert.toint32(dr["gradeid"]); gr.gradename=dr["gradename"].tostring(); list.add(gr); } } catch (exception ex) { throw new exception(ex.message); } } return list; } #endregion #endregion }} |
02.在業(yè)務(wù)邏輯層
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using system;using system.collections.generic;using system.linq;using system.text;using system.threading.tasks;using myschool.dal;using system.data;using myschool.model;namespace myschool.bll{ public class gradebll { gradedal gradedal = new gradedal(); #region 獲取年級(jí)數(shù)據(jù)，為在下拉框中顯示 public datatable selectgrade(string gradetype) { return gradedal.selectgrade(gradetype); } public datatable loadcombox() { return gradedal.loadcombox(); } public list<grade> loadcombox2() { return gradedal.loadcombox2(); } #endregion public list<grade> loadcombox3() { return gradedal.loadcombox3(); } }} |
03.在窗體ui層
在load事件中加載年級(jí)下拉框
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private void frmselectresult_load(object sender, eventargs e) { #region 加載年級(jí)下拉框 try { list<grade> list = gradedal.loadcombox3(); list.insert(0, new grade() { gradeid=-1,gradename="--全部--" }); cbograde.valuemember = "gradeid"; cbograde.displaymember = "gradename"; cbograde.datasource = list; } catch (exception ex) { messagebox.show(ex.message); } #endregion #region 加載科目下拉框 //try //{ // list2 = subjectdal.loadcomboxsub(); // list2.insert(0, new subject() { subjectid = -1, subjectname = "--全部--" }); // cbosubject.valuemember = "subjectid"; // cbosubject.displaymember = "subjectname"; // cbosubject.datasource = list2; //} //catch (exception ex) //{ // messagebox.show(ex.message); //} #endregion } |
其中在使用
獲得年級(jí)下拉框隱藏值得方法（2）
int num = convert.toint32(cbograde.selectedvalue);
加載年級(jí)下拉框時(shí)：會(huì)出現(xiàn)的錯(cuò)誤的寫(xiě)法
把cbograde.datasource = list;寫(xiě)在
cbograde.valuemember = "gradeid";
cbograde.displaymember = "gradename";上面
即：
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#region 加載年級(jí)下拉框 try { list<grade> list = gradedal.loadcombox3(); list.insert(0, new grade() { gradeid=-1,gradename="--全部--" }); cbograde.datasource = list; cbograde.valuemember = "gradeid"; cbograde.displaymember = "gradename"; } catch (exception ex) { messagebox.show(ex.message); } #endregion |
這是就會(huì)出現(xiàn)下面錯(cuò)誤：
在年級(jí)的selectedindexchanged事件中
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try { //根據(jù)年級(jí)取得科目信息并綁定 #region 獲得年級(jí)下拉框隱藏值得方法（1） grade sub = (grade)cbograde.selecteditem; int num =sub.gradeid; #endregion #region 獲得年級(jí)下拉框隱藏值得方法（2） // int num = convert.toint32(cbograde.selectedvalue.tostring()); #endregion list<subject> list = subjectdal.loadcomboxsub2(num); cbosubject.valuemember = "subjectid"; cbosubject.displaymember = "subjectname"; cbosubject.datasource = list; } catch (exception) { messagebox.show("出錯(cuò)"); } |
以上就是本文的全部?jī)?nèi)容，希望對(duì)大家學(xué)習(xí)c#程序設(shè)計(jì)有所幫助。
