求助 谢谢谢谢谢谢谢谢

我编了一个学生成绩录入程序但有错误，不会修改，请帮帮忙
Public Class Form2
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim id, name, age, grade As String
Dim count As Integer
id = Trim(TextBox1.Text)
name = Trim(TextBox2.Text)
grade = Trim(TextBox3.Text)
age = Trim(TextBox4.Text)

If id = "" Then
MessageBox.Show("学号不能为空")
Return
End If

Dim com As OleDb.OleDbCommand
Dim dr As OleDb.OleDbDataReader ' cmd.CommandText = _
' "SELECT * FROM Titles JOIN Publishers " _
' & "ON Publishers.PubId = Titles.PubID " _
' & "WHERE Publishers.State = 'CA'"
com = New OleDb.OleDbCommand
Dim conn As New OleDb.OleDbConnection

com.CommandText = _
("select count * from student " _
& "where student.id="id"") 错误提示:应为"）"

com.Connection = Conn
Conn.open()
dr = com.ExecuteReader
dr.Read()
count = dr.GetValue(0)
dr.Close()
If count <> 0 Then
MessageBox.Show("学号重复!请确认")
Else
com=new OleDb.OleDbCommand ("insert into student(id,name,age,grade)values("id"','"&name&"','"&age&"','"&grade&"')"),conn) 错误提示：应为逗号、“）”或有效的表达式继续符


End If
com.Dispose()
conn.close()
End Sub
End Class


Public Class Form3

Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim conn As New OleDb.OleDbConnection
Dim com As New OleDb.OleDbCommand("select course from course order by c_id".conn)
Dim dr As OleDb.OleDbDataReader 错误提示："conn"不是"string"的成员

Dim course As String

Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyValue = 13 Then
Dim id As String
Dim count As Integer
id = Trim(TextBox1.Text)
Dim com As New OleDb.OleDbCommand
dim com as New OleDb.OleDbCommand("select count(*)from student where id='"&id&"'",conn)
Dim dr As OleDb.OleDbDataReader 错误提示：应为逗号、“）”或有效的表达式继续符



End If
End Sub


Private Sub OleDbConnection1_InfoMessage(ByVal sender As System.Object, ByVal e As System.Data.OleDb.OleDbInfoMessageEventArgs) Handles OleDbConnection1.InfoMessage

End Sub
End Class

Public Class Form5

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Dim id, course As String
id = Trim(TextBox1.Text)
course = Trim(ComboBox1.SelectedItem)
If id = "" Then
MessageBox.Show("请输入学号!")
Return

End If
If course = "" Then
MessageBox.Show("请选择课程!")
Return
End If
Dim com As New OleDb.OleDbCommand
Dim dr As OleDb.OleDbDataReader
Dim conn As New OleDb.OleDbConnection
com.Connection = conn
com.CommandText = _
"select mark from stumark,student where stumark.id=student.id and student.id='" _
id"'and stumark.c_id=(select c_id from course where course='"&course&") _
错误提示：应为语句结束
conn.open()
dr = com.ExecuteReader
dr.Read()
TextBox4.Text = Trim(dr.GetString(0))
dr.Close()
com.Dispose()
conn.close()
Button1.Enabled = True

End Sub