VB.NET把多个combobox条件查询到的数据一起用datagridview显示,为什么我的点查询后datagridview不显示数据。

[qq_43495831]

VB.NET把多个combobox条件查询到的数据一起用datagridview显示,为什么我的点查询后datagridview不显示数据。

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

[兔子-顾问]

看到你这Button6，ComboBox1，ComboBox2，ComboBox3就来气，除非应付考试和作业，否则早点改掉这臭毛病，控件拖出来就立刻命名，否则你回头看一行都是没意义的控件名，鬼知道是什么内容。 看代码应该不至于不会排错，如果累了就出去走走，静下心来再看代码，仔细分析下原因，不显示？还是查询没有结果？还是有报错？顺着这个思路，逐条加断点去看运行到某处的变量是否是你期待的，比如查查sql语句，不论对不对了，只要不报错可能就是格式没错，但逻辑有问题，复制出来到数据库软件中去执行一下，调好sql语句再回来看拼接的对不对。 思路如此，代码质量太低，没耐心看，自己调试一下。

[SeaSky606]

建议你在DA.Fill这一行建立断点，运行程序后，查看DA的内的SQL语句