VB.NET编程 ExecuteNonQuery: CommandText 属性尚未初始化

要实现将文本框和组合框中的数据更新到SQL数据库
代码： Dim con As New SqlClient.SqlConnection
con = Helper.getSqlConnection()
con.Open()
Dim a(6, 3) As Integer
Dim i As Integer

For i = 1 To 6
a(i, 3) = ComboBox(i).selectvalue
Next i
a(1, 1) = Val(TextBox1.Text)
a(1, 2) = Val(TextBox2.Text)
a(2, 1) = Val(TextBox3.Text)
a(2, 2) = Val(TextBox4.Text)
a(3, 1) = Val(TextBox5.Text)
a(3, 2) = Val(TextBox6.Text)
a(4, 1) = Val(TextBox7.Text)
a(4, 2) = Val(TextBox8.Text)
a(5, 1) = Val(TextBox9.Text)
a(5, 2) = Val(TextBox10.Text)
a(6, 1) = Val(TextBox1.Text)
a(6, 2) = Val(TextBox1.Text)

For i = 1 To 6
Dim cmdtext As String = "insert into time(location,min,max,type) values (" + i.ToString + "," + a(i, 1).ToString + a(i, 2).ToString + "," + a(i, 3).ToString + ")"
Next i
cmd = New SqlClient.SqlCommand(cmdtext, con)
cmd.ExecuteNonQuery()
con.Close()

Helper是什么？
con需要连接字符串的，一般在构造函数中带连接字符串哦
比如Dim con As New SqlClient.SqlConnection("Data Source=192.168.0.210;Initial Catalog=TileDB;User ID=sa;Password=123456;connect timeout=30")

第一问：您可以在查询的时候判断是否已经查到记录，必须保证能够查到记录以后才允许编辑，比如： dim myselectquery as string = "select * from 用户信息 where 姓名='" & textbox8.text & "'" oledbdataadapter1.selectcommand.commandtext = myselectquery oledbdataadpater.selectcommand.connection.open() if(oledbdataadapter1.selectcommand.executereader().hasrows) then '判断可以查到吗？ dataset11.clear() oledbdataadapter1.fill(dataset11, "通讯数据") end if oledbdataadpater.selectcommand.connection.close() 第二问：如果你生成了oledbdataadapter.updatacommand的命令，直接更新的时候使用：oledbdataadapter.update() 如果手动，oledbdataadapter1.updatecommand.commandtext = "update table set 字段1=@字段1，字段2=字段2…… where 主键字段=@主键字段" using cmd as new oledb.oledbdataadapter cmd.updatecommand.commandtext = "update table set 字段1=@字段1，字段2=字段2,主键字段=@新主键字段,…… where 主键字段=@旧主键字段" cmd.updatecommand.parameters.add("@字段1", oledb.oledbtype.varchar, 20, "对应datatable中的更新字段") …… cmd.updatecommand.parameters.add("@旧主键字段", oledb.oledbtype.integer, "对应datatable中的更新字段") cmd.updatecommand.parameters("@旧主键字段").sourceversion = datarowversion.original end using 更新：oledbdataadapter1.update("通讯数据")