Visual Basic

3-Feb-09 20:09

I have been programming with VB6 for many years and I am now in the process of “upgrading” to VB2008. I want to do all my work with code and not with data controls. (See my attached code so far). This is a useless sample just to get my head around a few things.
1. In the scores group on my form, I have 3 textboxes binded to my “BindingManagerBase” I can now move up and done both tables. I want to add “Delete”, “Add” and “Edit” functionality for the Scores table. Instead of manually looking up the StudentID, I want to replace the textbox with a Combobox. So I want to see the student’s “FirstName” from the students table in the combo box, and then link the StudentID from the Student Table to the StudentID in the TestScores table. (I have done it many times with VB6, but how do I do it in VB2008.

This is my tables and my code.

Table Name: Students
StudentID FirstName LastName
1 Amy Anderson
2 Bob Baker
3 Cindy Carter
4 Donald Dorph

Table Name: TestScores
StudentID TestNumber Score
1 1 98
1 2 94
2 1 74
3 2 65

' Data adapter for the Students table.
Dim m_daStudents As New OleDbDataAdapter( _
"SELECT Students.StudentID, Students.FirstName, Students.LastName " & _
"FROM Students", _
"PROVIDER=MSDataShape;" & _
"Data PROVIDER=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source='Student Scores.mdb';" & _
"Persist Security " & _
"Info=False")
' Data adapter for the TestScores table.
Dim m_daTestScores As New OleDbDataAdapter( _
"SELECT TestScores.StudentID, TestScores.TestNumber, TestScores.Score " & _
"FROM TestScores", _
"PROVIDER=MSDataShape;" & _
"Data PROVIDER=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source='Student Scores.mdb';" & _
"Persist Security " & _
"Info=False")
' The DataSet.
Dim m_DataSet As New DataSet("Student Scores")
' Declare a binding manager field
Public bm_Students As BindingManagerBase
Public bm_TestScores As BindingManagerBase

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Load the Students table.
m_daStudents.Fill(m_DataSet, "Students")
' Load the TestScores table.
m_daTestScores.Fill(m_DataSet, "TestScores")
' Get the DataTable objects.
Dim dt_students As DataTable = m_DataSet.Tables("Students")
Dim dt_testscores As DataTable = m_DataSet.Tables("TestScores")

' Get DataColumn objects we will need.
Dim col_students_studentid As DataColumn = _
dt_students.Columns("StudentId")
Dim col_testscores_studentid As DataColumn = _
dt_testscores.Columns("StudentId")
Dim col_testscores_testnumber As DataColumn = _
dt_testscores.Columns("TestNumber")

' Define the primary keys.
Dim students_keys() As DataColumn = _
{col_students_studentid}
dt_students.PrimaryKey = students_keys

Dim testscores_keys() As DataColumn = _
{col_testscores_studentid, col_testscores_testnumber}
dt_testscores.PrimaryKey = testscores_keys

' Make a foreign key constraint.
Dim fk_studentid As New ForeignKeyConstraint( _
col_students_studentid, col_testscores_studentid)
dt_testscores.Constraints.Add(fk_studentid)

' Bind to textboxes for Students table
txtStudentID.DataBindings.Add("text", m_DataSet, "Students.StudentID")
txtFirstName.DataBindings.Add("text", m_DataSet, "Students.FirstName")
txtLastName.DataBindings.Add("text", m_DataSet, "Students.LastName")

' Bind to textboxes for TestScore table
txtTestScores1.DataBindings.Add("text", m_DataSet, "TestScores.StudentID")
txtTestScores2.DataBindings.Add("text", m_DataSet, "TestScores.TestNumber")
txtTestScores3.DataBindings.Add("text", m_DataSet, "TestScores.Score")

' Bind to datagrid for TestScore table
DataGridView1.DataSource = m_DataSet
DataGridView1.DataMember = "TestScores"

bm_Students = BindingContext(m_DataSet, "Students")
bm_Students.Position = 0
bm_TestScores = BindingContext(m_DataSet, "TestScores")
bm_TestScores.Position = 0

End Sub

Jay Royall4-Feb-09 5:56

4-Feb-09 5:56

Have you tried binding the combobox to the datatable?
i.e.

ComboBox.DisplayMember = FieldToDisplay
ComboBox.ValueMember = ValueField
ComboBox.DataSource = DataTable

Jaco Muller4-Feb-09 11:20

4-Feb-09 11:20

Thank you for your time. Yes, I have tried but it did not work. The syntax might be wrong. From VB6 I know that there are 5 properties to set:
1. You need to specify the table for the displayed value. (Table: Students)
2. You need to specify the field of the displayed value. (Field: FirstName)
3. You need to specify the field to transfer. (Field: StudentID)
4. You need to specify the table to be updated. (Table: Testscores)
5. You need to specify the field to be updated with the ComboBox. (Field: StudentID)
So maybe my downfall is thinking in VB6.
Back to your recommendation:
ComboBox.DisplayMember = FieldToDisplay What will this be in my case, based on the code
ComboBox.ValueMember = ValueField What will this be in my case, based on the code
ComboBox.DataSource = DataTable What will this be in my case, based on the code
Thank again for your time

Jay Royall4-Feb-09 22:37

4-Feb-09 22:37

Being a beginner myself I'm not that familiar with DataTables, but I think it should be something like:

ComboBox.DisplayMember = "Firstname"
ComboBox.ValueMember = "StudentId"
ComboBox.DataSource = dt_students

Hope this helps.

Jaco Muller4-Feb-09 23:04

4-Feb-09 23:04

Thanks again for your time, I will try it tomorrow, I am not at my computer at the moment. Do you have an idea how to search for a record? Say for example I have a textbox and I enter a name in the textbox. I then want to go directly to record without looping through the table?

Jay Royall4-Feb-09 23:33

4-Feb-09 23:33

Again, being a beginner I may be wrong here but I think you can use the Select function to filter the rows in your datatable. Something like:

dt_Students.Select("FirstName = John")

Jaco Muller5-Feb-09 11:47

5-Feb-09 11:47

Sorry, back to your last advice. This fills the combobox, but it is not linked to the Scores table. So if I hit the next button, I can step through the table, but the combobox will not reflect the correct student, it will stay with the first name.

Jay Royall5-Feb-09 23:57

5-Feb-09 23:57

Well if I understand you correctly, you need to handle the click event of the next button and then select the correct item in the ComboBox using: ComboBox.selectedValue = StudentID

Jaco Muller6-Feb-09 0:09