全部代码：
Public Class Studentclassenquiry
Dim objConn As New MySqlConnection
Dim objComm As New MySqlCommand
Dim DA As New MySqlDataAdapter
Dim DS As New DataSet
'objConn.ConnectionString = My.Forms.Login.Conn
Private Sub Studentclassenquiry_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
objConn.ConnectionString = My.Forms.Login.Conn
DS.Tables.Clear()
DS.Clear()
DA = New MySqlDataAdapter("select * from camnpus ", objConn)
DA.Fill(DS, "camnpus")
'ComboBox1.DataSource = DS.Tables(0)
ComboBox1.DisplayMember = "Caname"
ComboBox1.ValueMember = "CaId"
ComboBox1.DataSource = DS.Tables(0)
End Sub
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
DS.Tables.Clear()
DS.Clear()
DA = New MySqlDataAdapter("select * from building where CamId='" & ComboBox1.SelectedValue.ToString() & "'", objConn)
DA.Fill(DS, "building")
ComboBox2.DisplayMember = "Bname"
ComboBox2.ValueMember = "BId"
ComboBox2.DataSource = DS.Tables(0)
End Sub
Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
DS.Tables.Clear()
DS.Clear()
objConn.Open()
DA = New MySqlDataAdapter("select * from classroom where BuiId='" & ComboBox2.SelectedValue.ToString() & "'", objConn)
DA.Fill(DS, "classroom")
ComboBox3.DisplayMember = "Came"
ComboBox3.ValueMember = "CId"
ComboBox3.DataSource = DS.Tables(0)
objConn.Close()
End Sub
Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
objConn.ConnectionString = My.Forms.Login.Conn
DS.Tables.Clear()
DS.Clear()
Dim dt As New DataTable
objConn.Open()
DA = New MySqlDataAdapter("select CamId as 校区,BuId as 教学楼,ClassId as 教室编号,Classname as 教室名称, UseId as 使用者编号,UseBegin as 开始时间,UseEnd as 结束时间,Userstatus as 使用者类型 from byclassroom where BuId='" & ComboBox2.SelectedValue.ToString() & "'AND ClassId='" & ComboBox3.SelectedValue.ToString() & "'", objConn)
DA.Fill(DS, "byclassroom")
dt = DS.Tables("byclassroom")
objConn.Close() '关闭数据库
DataGridView1.AutoGenerateColumns = True '自动创建列
DataGridView1.DataSource = dt
End Sub
End Class
