--事务的使用示例 create database MyDB go use MyDB create table account ( Id int identity primary key, balance int --余额 ) insert into account values(1000) insert into account values(200) go --在存储过程中使用事务,简单转帐 create procedure transfer(@fromId int, @toId int, @total int) as begin declare @ts varchar(30), @tb int begin transaction update account set balance=balance+@total where id=@toId update account set @tb=balance, balance=balance-@total where id=@fromId if (select balance from account where id=@fromId)>=0 commit transaction else begin set @ts=convert(varchar(30), @total) --int类型转换为字符串,(30)可省略 raiserror('余额%d不足以转帐%s', 16, 1, @tb, @ts)--%d,%s为格式控制符 rollback transaction end end go exec transfer 1, 2, 1234 --测试,转帐不成功 select * from account exec transfer 1, 2, 500 --测试,转帐成功 select * from account
//WinForm实现中的若干问题 //单击DataGridView控件(名为dgvUser)时,把当前行的数据填充到文本框控件的方法 private void dgvUser_Click(object sender, EventArgs e) { txtUserName.Text = dgvUser.CurrentRow.Cells[0].Value.ToString(); txtDescription.Text = dgvUser.CurrentRow.Cells[1].Value.ToString(); txtPassword.Text = dgvUser.CurrentRow.Cells[2].Value.ToString(); txtAuthority.Text = dgvUser.CurrentRow.Cells[3].Value.ToString(); } //设置DataGridView控件(名为dgvUser)第三列不可见的语句 dgvUser.Columns[2].Visible = false; //设置Button控件(名为btnInsert)不可用的语句 btnInsert.Enabled = false; //控制只有一个子窗体(名为frmUser)的方法 //设置主窗体的IsMdiContainer为True,WindowState为Maximized //menuUser为菜单项名 private void menuUser_Click(object sender, EventArgs e) { foreach (Form frm in this.MdiChildren)//关闭所有子窗体 { frm.Close(); } frmUser myFrmUser = new frmUser(); myFrmUser.MdiParent = this;//设置为子窗体 myFrmUser.WindowState = FormWindowState.Maximized;//最大化 myFrmUser.Show(); } //登录窗体(不要作为子窗体)关闭后才能做其他事情及菜单控制的方法 private void cotrolMenu(string auth)//自定义函数,需据实际情况修改 { if (auth == "0") { menuUser.Visible = true; menuReader.Visible = true; } else { menuUser.Visible = false; menuReader.Visible = false; } } private void menuLogin_Click(object sender, EventArgs e) { myfrmLogin=new frmLogin(); myfrmLogin.ShowDialog();//将窗体显示为模式对话框 cotrolMenu(myClass.Authority);//myClass为类名,Authority为其中定义的公有变量 } //确认退出程序的方法,删除确认类似 private void frmMain_FormClosing(object sender, FormClosingEventArgs e) { if (MessageBox.Show("Really Exit?", "Confirm Exit", MessageBoxButtons.YesNo,MessageBoxIcon.Question) == DialogResult.No) { e.Cancel = true; } }