I need to bind a DataGridView to a many-to-many Relation.
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I know how to create both of the one-to-many Relations:
I know how to bind a DataGrid view to a Relation, for example:
How do I create a many-to-many Relation and use it for binding a DataGridView?
For example, I have a form that is bound to the VendorTypes DataTable via a BindingSource (bsVendorTypes). When the bsVendorTypes.PositionChanged method is called, I want the Vendors DataGridView (dgvVendors) to automatically show the Vendors that are related to the current VendorType.
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In the above example, I am populating a temporary DataTable (dtTemp) via a temporary DataAdapter (dad) and then binding Vendors DataGridView (dgvVendors) to dtTemp DataTable.
I want to use the many-to-many Relation instead of reading the data from the underlying MS Access database via a DataAdapter.
I know how to create both of the one-to-many Relations:
Code:
'VendorTypes and VendorMembers
dsMain.Relations.Add("VendorTypes_VendorMembers", dsMain.Tables("VendorTypes").Columns("RecID"), dsMain.Tables("VendorMembers").Columns("VendorTypeID"))
fkc = dsMain.Relations("VendorTypes_VendorMembers").ChildKeyConstraint
fkc.DeleteRule = Rule.Cascade
fkc.UpdateRule = Rule.Cascade
fkc.AcceptRejectRule = AcceptRejectRule.None
'Vendors and VendorMembers
dsMain.Relations.Add("Vendors_VendorMembers", dsMain.Tables("Vendors").Columns("RecID"), dsMain.Tables("VendorMembers").Columns("VendorID"))
fkc = dsMain.Relations("Vendors_VendorMembers").ChildKeyConstraint
fkc.DeleteRule = Rule.Cascade
fkc.UpdateRule = Rule.Cascade
fkc.AcceptRejectRule = AcceptRejectRule.NoneCode:
With bsFuel
.DataSource = Nothing
.DataMember = "Vehicle_Fuel" '...bind to relationship (before setting the DataSource property, which fires the PositionChanged() event of the BindingSource)
.DataSource = bsVehicles '...fires the BindingSource's PositionChanged() event
.Sort = "VehicleID, Odometer"
End With
If flgDebug Then Debug.WriteLine("bsFuel datasource has " & bsFuel.Count & " items.")
dgvFuel.DataSource = bsFuelFor example, I have a form that is bound to the VendorTypes DataTable via a BindingSource (bsVendorTypes). When the bsVendorTypes.PositionChanged method is called, I want the Vendors DataGridView (dgvVendors) to automatically show the Vendors that are related to the current VendorType.
In the above example, I am populating a temporary DataTable (dtTemp) via a temporary DataAdapter (dad) and then binding Vendors DataGridView (dgvVendors) to dtTemp DataTable.
Code:
strSQL = "SELECT Vendors.* " &
"FROM Vendors INNER JOIN VendorMember ON Vendors.RecID = VendorMember.VendorID " &
"WHERE (VendorMember.VendorTypeID = " & lngVendorID & ") " &
"ORDER BY Vendors.VendorName, Vendors.VendorCity, Vendors.VendorState"
If con.State <> ConnectionState.Open Then con.Open()
Using dad As New OleDb.OleDbDataAdapter(strSQL, con)
dad.Fill(dtTemp)
End Using
con.Close()
dgvVendors.DataSource = dtTemp
lblGridInfo.Text = "Vendors (" & dgvVendors.Rows.Count & CStr(IIf(dgvVendors.Rows.Count = 1, " item", " items")) & "):"