Bound datatgridview not saving changes to tableadapter, and thus not to database - vb.net

Question

I have a datagridview bound to a table that seems to work fine, but will not save changes to the database. I am using the same code as I used in another project, which did save changes, so I am flummoxed. Also, I have debugged and the save code is being called, just not working. The code in the form calls a separate class with business logic.
Code in the form below:
Private Sub frmAdminAssign_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' Below is generated by Visual Studio when I select my data source for my datagridview
Credit_adminTableAdapter.Fill(DataSet1.credit_admin) ' Foreign key relationship to table being updated (lookup table).
LoanTableAdapter.Fill(DataSet1.loan) ' Table being updated
admin_assign = New AdminAssign()
admin_assign.FilterUnassigned(dgvAssign, LoanTableAdapter)
End Sub
Private Sub dgvAssign_CellEndEdit(sender As Object, e As DataGridViewCellEventArgs) Handles dgvAssign.CellEndEdit
admin_assign.SaveAssignmentChanges(DataSet1, LoanTableAdapter)
End Sub
Below is code in business logic class called from above:
Public Sub SaveAssignmentChanges(ByRef data_set As DataSet1, ByRef loan_table_adapter As DataSet1TableAdapters.loanTableAdapter)
' Saves changes to DB.
Dim cmdBuilder As SqlCommandBuilder
cmdBuilder = New SqlCommandBuilder(loan_table_adapter.Adapter)
loan_table_adapter.Adapter.UpdateCommand = cmdBuilder.GetUpdateCommand(True)
Try
loan_table_adapter.Adapter.Update(data_set)
Catch unknown_ex As Exception
Dim error_title As String = "Database Save Error"
Dim unknown_error As String = $"There was an error saving to the database.{vbNewLine}Error: {unknown_ex.ToString}"
MessageBox.Show(unknown_error, error_title, MessageBoxButtons.OK, MessageBoxIcon.Warning)
End Try
End Sub
The data from the datagridview is not saving to the tableadapter, which I found out by adding the lines below in the start of the second procedure:
Dim x As String = loan_table_adapter.GetData()(0)("note_number") ' Unchanged, check was right row
Dim y As String = loan_table_adapter.GetData()(0)("credit_admin_id") ' Changed in datagridview but still null (get null error)

Answer 1

I figured it out, it was related to a filter routine that is not above where I passed a tableadapter byref when I should have passed a datatable byval. So, related to one of jmcilhinney's byref vs byval comments above. See problem code below:
Public Sub FilterUnassigned(ByRef dgv_assigned As DataGridView, loan_table_adapter As DataSet1TableAdapters.loanTableAdapter)
' Should have passed in DataSet1.loan DataTable ByVal and used it below:
Dim unassigned_loans As DataView = loan_table_adapter.GetData().DefaultView()
unassigned_loans.RowFilter = "request_date Is Not Null AND numerated_assigned_user Is Null"
dgv_assigned.DataSource = unassigned_loans
End Sub
Also, skipping the SQLCommandBuilder commands and my code still works. So, all I need is one line as per jmcilhinney instead of 4 (excl error handling) as per below:
Try
loan_table_adapter.Update(data_set)
Catch unknown_ex As Exception
Dim error_title As String = "Database Save Error"
Dim unknown_error As String = $"There was an error saving to the database. Please contact Kevin Strickler to resolve.{vbNewLine}Error: {unknown_ex.ToString}"
MessageBox.Show(unknown_error, error_title, MessageBoxButtons.OK, MessageBoxIcon.Warning)
End Try