//开发工具：Microsoft Visual Studio 2005
//数据库:Microsoft SQL Server 2005
//说明：这里建立的数据库名为Demo,有一个学生表Student,为操作方便起见,我只添加两个字段:studentnum和studentname.//二、代码：//1.引入名称空间:using System.Data.SqlClient;//2.定义连接字符串,连接对象，命令对象://private String connectionstr;// private SqlConnection connection;// private SqlCommand command;//3.在构造函数中初始化连接字符串，连接对象，命令对象
//(1)初始化连接字符串：// 方式① connectionstr="server=localhost;uid=sa;pwd=123456;database=Demo"; // 方式② connectionstr="server=127.0.0.1";Integrade Security=SSPI;database=Demo";// 其中，SIMS是我要连接的数据库名.(1)中的uid 和pwd是你登录数据库的登录名和密码 // 注：这种连接是连接本地的数据库，若要连接局域网内其它机子上的数据库，可将方式①的"server=localhost;"改为"server=数据库所在机子的IP;"// (2)初始化连接对象 connection = new SqlConnection(connectionstr);// (3)初始化命令对象 command =new SqlCommand(); command .Connection =connection ;//4.操作数据库中的数据// (1)查询数据库中的数据// 方法一： string snum=tBstudentnum .Text .Trim (); string str = "select * from Student where studentnum='" + snum + "'"; command .CommandText =str; connection.Open(); if (command.ExecuteScalar() == null) { MessageBox.Show("您输入的学号对应的学生不存在！", "错误", MessageBoxButtons.OK,MessageBoxIcon.Error); } else { SqlDataReader sdr = command.ExecuteReader(); while (sdr.Read()) { tBstudentnum .Text = sdr["studentnum"].ToString(); tBstudentname.Text = sdr["studentname"].ToString(); } sdr.Close(); } connection.Close();//方法二： string snum=tBstudentnum .Text .Trim (); string str = "select * from Student where studentnum='" + snum + "'"; command .CommandText =str; connection.Open(); if (command.ExecuteScalar() == null) { MessageBox.Show("您输入的学号对应的学生不存在！", "错误",MessageBoxButtons.OK,MessageBoxIcon.Error); } else { SqlDataAdapter sda = new SqlDataAdapter(str,connection ); DataSet ds = new DataSet(); sda.Fill(ds, "Student"); DataTable dt = ds.Tables["Student"]; tBstudentnum.Text = dt.Rows[0]["studentnum"].ToString(); tBstudentname.Text = dt.Rows[0]["studentname"].ToString(); } connection.Close(); //(2)向数据库中添加数据//方法一: string snum = tBstudentnum.Text.Trim (); string sname = tBstudentname.Text.Trim(); if (snum == "" || sname == "") { MessageBox.Show("学生学号或姓名不能为空！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { string insertstr="insert into Student values('"+snum +"','"+sname +"')"; command.CommandText = insertstr; connection.Open(); command.ExecuteNonQuery(); MessageBox.Show("学生添加成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); connection.Close(); }// 方法二: string str = "select * from Student"; string insertstr = "insert into Student values('" + snum + "','" + sname + "')"; SqlDataAdapter sda = new SqlDataAdapter(str, connection); DataSet ds = new DataSet(); sda.Fill(ds, "Student"); DataTable dt = ds.Tables["Student"]; DataRow dr = dt.NewRow(); dr["studentnum"] = snum; dr["studentname"] = sname; dt.Rows.Add(dr); sda.InsertCommand = new SqlCommand(insertstr, connection); sda.Update(ds, "Student"); MessageBox.Show("学生添加成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); //(3)修改数据库中的数据// 方法一: string snum = tBstudentnum.Text.Trim(); string sname = tBstudentname.Text.Trim(); if (snum == "" || sname == "") { MessageBox.Show("学生学号或姓名不能为空！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { string modifystr = "update Student set studentname='" + sname + "' where studentnum='" + snum + "'"; command.CommandText = modifystr; connection.Open(); command.ExecuteNonQuery(); MessageBox.Show("学生的姓名修改成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information ); connection.Close(); // 方法二: string snum = tBstudentnum.Text.Trim(); string sname = tBstudentname.Text.Trim(); if (snum == "" || sname == "") { MessageBox.Show("学生学号或姓名不能为空！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { string str = "select * from Student where studentnum='" + snum + "'"; ; string updatestr = "update Student set studentname='" + sname + "' where studentnum='" + snum + "'"; SqlDataAdapter sda = new SqlDataAdapter(str, connection); DataSet ds = new DataSet(); sda.Fill(ds, "Student"); DataTable dt = ds.Tables["Student"]; dt.Rows[0]["studentname"] = sname; sda.UpdateCommand = new SqlCommand(updatestr , connection); sda.Update(ds, "Student"); MessageBox.Show("学生姓名修改成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); }//(4)删除数据库中的数据//方法一: string snum = tBstudentnum.Text.Trim(); if (snum == "") { MessageBox.Show("学生学号不能为空！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { string str = "select * from Student where studentnum='" + snum + "'"; string deletestr = "delete from Student where studentnum='" + snum + "'"; command.CommandText =str ; connection.Open(); if (command.ExecuteScalar() == null) { MessageBox.Show("此学号对应的学生不存在！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { command.CommandText = deletestr; command.ExecuteNonQuery(); MessageBox.Show("学生的信息删除成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); } connection.Close(); //方法二: string str = "select * from Student where studentnum='" + snum + "'"; string deletestr = "delete from Student where studentnum='" + snum + "'"; SqlDataAdapter sda = new SqlDataAdapter(str, connection); DataSet ds = new DataSet(); sda.Fill(ds, "Student"); DataTable dt = ds.Tables["Student"]; if (dt.Rows.Count > 0) { dt.Rows[0].Delete(); sda.DeleteCommand = new SqlCommand(deletestr, connection); sda.Update(ds, "Student"); MessageBox.Show("学生信息删除成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); } else { MessageBox.Show("此学号对应的学生不存在！", "错误",MessageBoxButtons.OK, MessageBoxIcon.Error); }//注：以上对数据库的操作,大都从操作角度出发仅进行单一的操作,有的地方并未进行错误处理,如修改学生信息时,学号应不可能编辑等
