选课系统VB.NET

VB.NET 包含access数据库 If txtName.Text = "" Then MsgBox("请输入用户名") txtName.Focus() txtPassword.Text = "" Exit Sub End If If txtPassword.Text = "" Then MsgBox("请输入密码") txtPassword.Focus() txtName.Text = "" Exit Sub End If sqlstr = "select * from users where 学号 = '" & txtName.Text & "'and 密码 = '" & txtPassword.Text & "'" '从大到小顺序排列顺序固定格式，注意：学号为字符型必须用单引号引住" connection.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=SelectCourse.mdb" adapter = New OleDbDataAdapter(sqlstr, connection) dataSet = New DataSet adapter.Fill(dataSet) '所以oledbDataAdapter填充到dataset1的只是文本框中的学号对应的那一行 If dataSet.Tables(0).Rows.Count 0 Then '如果dataset1所填充的数据表所对应的行的个数为0 则提示没有这个学生 t = txtName.Text txtName.Text = "" txtPassword.Text = "" txtName.Focus() Me.Hide() frmMain.ShowDialog() Else txtPassword.Text = "" txtName.Text = "" txtName.Focus() i += 1 If i < 3 Then '三次错则自动退出程序 MessageBox.Show("你输入的用户名或密码不对,请重新输入", "error") '如果用户名输入的用户名或密码不对则提示用户重新输入 Exit Sub Else MsgBox("您是非法用户") End End If End If