Percy Kumah Percy Kumah - 3 months ago 23x Question

Filter a DataGridView without losing unbound changes

Im developing a application and I have a dgv which displays a list of employees. The dgv has an unbound checkbox column which is used in selecting employees for a required action. I use rowFilter to filter the list by department or location or whatever the user chooses.

If the user filters using Department 1 and checks the checkboxes next to the employees he wants, to select them and then filters to Department 2, to select a few more employees, when we filter back to Department 1, the checked employees aren't checked any more.

How can I make it such that once an employee is checked, you can filter with other parameters with losing the earlier selections. Im thinking of saving the checked state of each employee to the database before the next filter but I feel is possibly a quicker easier way. Is there?

This is the code I'm using to fill the dgv

sql = "SELECT employee_paysetup.EmployeeNumber AS EmployeeNo, employee_paysetup.FName, employee_paysetup.MName, " _
& "employee_paysetup.LName, (case when employee_paysetup.MName = ' ' then concat(employee_paysetup.FName,' ' , employee_paysetup.LName) else " _
& "concat(employee_paysetup.FName,' ' , employee_paysetup.MName,' ' , employee_paysetup.LName) end) " _
& "AS FullName, costcenters.CostCenterName AS cosName, departments.DepartmentName AS depName, " _
& "positions.PositionName AS posName, locations.LocationName AS locName, CostCenter, Department, Position, EmployeeLocation, PayGroup " _
& "FROM ((((((employee_paysetup LEFT JOIN employees ON employee_paysetup.EmployeeNumber = employees.EmployeeNumber) " _
& "LEFT JOIN costcenters ON employees.CostCenter = costcenters.CostCenterID) " _
& "LEFT JOIN departments ON employees.Department = departments.DepartmentID) " _
& "LEFT JOIN positions ON employees.Position = positions.PositionID) " _
& "LEFT JOIN locations ON employees.EmployeeLocation = locations.LocationID) " _
& "LEFT JOIN paygroups ON employee_paysetup.PayGroup = paygroups.ID) " & filterValue
cmd = New MySqlCommand(sql, conn)
cmd.Parameters.AddWithValue("@Status", "ACTIVE")
da.SelectCommand = cmd
dt.DefaultView.Sort = "FullName ASC"
dgvEmployees.DataSource = dt.DefaultView

And I filter using

dt.DefaultView.RowFilter = "myFilter"


The problem is that there us no storage provided for the unbound column. A fairly simple way of doing is to use the DataTable. Add a Selected column via SQL so that a column is created for it in the DataTable. This SQL adds a column named Selected to the DataTable:

Dim sql = "SELECT False As Selected, Id, Name, Descr, Bird, Color, ItemDate FROM Sample"

With most DBProviders this will work fine: The table will have a Boolean column and the DGV will add a check column for it. But there is a slight problem for MySQL since it lacks a way to CAST to Boolean. The simplest way is to skip the SQL Selected column and add a new column to the table:

' after the DS is built, but BEFORE it is bound to the DGV:
Dim dc As New DataColumn("Selected", GetType(Boolean))
dc.DefaultValue = False    ' important!
dc.SetOrdinal(0)           ' make it column 0

It is important that you do this after the DataSource/DataTable is built but before you bind it to the DGV. Also be sure to set the DefaultValue to something or else it will be DBNull for all the rows and choke the check column.

For MySQL, you can also catch and replace the Text column for a Check column in the ColumnAdded event.

Either way NET knows it is a "virtual" column, so it will not interfere with any DBCommand objects you may have built for the DataAdapter (the OP cant have any based on that query, but future readers may). Results:

enter image description here

I check-selected several orange and Stork records, then filtered and the checks remained. At the core, this and Mr CrowCoder's answer do the same thing just differently: provide somewhere to store the Selected state.

This method uses the DGV's natuaral ability to automatically save to the DataTable.

If you want to use the ColumnAdded event:

If e.Column.Name = "Selected" AndAlso TypeOf e.Column Is DataGridViewTextBoxColumn Then
    Dim dc As New DataGridViewCheckBoxColumn()
    dc.HeaderText = "Selected"
    dc.Name = "Selected"
    dc.DataPropertyName = "Selected"
    dc.ValueType = GetType(Boolean)
    dgv5.Columns.Insert(0, dc)
    dc.DisplayIndex = 0
End If

The really important thing is to assign the DataPropertyName so the DGV knows where in the table to store the data.

Directly adding a column to the DataTable is more direct, I often use the ColumnAdded method just because there are usually one or two other tweaks.