C#

valueType.Rows.Add(new object[] {100, "Distance"});

valueType.Rows.Add(new object[] {500, 100, "km"});
valueUnitOfMeasurement.Rows.Add(new object[] {501, 100, "m"});
valueUnitOfMeasurement.Rows.Add(new object[] {502, 100, "cm"});
valueUnitOfMeasurement.Rows.Add(new object[] {503, 100, "mm"});

public partial class Form1 : Form
    {
        DataTable tblPrimary, tblSecondary;
        BindingSource primaryBS, filteredSecondaryBS, unfilteredSecondaryBS;
        
        public Form1()
        {

            tblPrimary = new DataTable("Primary");
            tblPrimary.Columns.Add("ID", typeof(int));
            tblPrimary.Columns.Add("Name", typeof(string));

            tblSecondary = new DataTable("Secondary");
            tblSecondary.Columns.Add("ID", typeof(int));
            tblSecondary.Columns.Add("subID", typeof(int));
            tblSecondary.Columns.Add("Name", typeof(string));

            tblPrimary.Rows.Add(new object[] { 0, "Force" });
            tblPrimary.Rows.Add(new object[] { 1, "Torque" });
            tblPrimary.Rows.Add(new object[] { 2, "Pressure" });

            tblSecondary.Rows.Add(new object[] { 0, 0, "lb" });
            tblSecondary.Rows.Add(new object[] { 1, 0, "N" });
            tblSecondary.Rows.Add(new object[] { 2, 0, "oz" });
            tblSecondary.Rows.Add(new object[] { 3, 1, "in-lb" });
            tblSecondary.Rows.Add(new object[] { 4, 1, "ft-lb" });
            tblSecondary.Rows.Add(new object[] { 5, 1, "N-m" });
            tblSecondary.Rows.Add(new object[] { 6, 2, "PSI" });
            tblSecondary.Rows.Add(new object[] { 7, 2, "Pa" });
            tblSecondary.Rows.Add(new object[] { 8, 2, "bar" });
            
            InitializeComponent();

            primaryBS = new BindingSource();
            primaryBS.DataSource = tblPrimary;
            primaryComboBoxColumn.DataSource = primaryBS;
            primaryComboBoxColumn.DisplayMember = "Name";
            primaryComboBoxColumn.ValueMember = "ID";

            // the ComboBox column is bound to the unfiltered DataView
            unfilteredSecondaryBS = new BindingSource();
            DataView undv = new DataView(tblSecondary);
            unfilteredSecondaryBS.DataSource = undv;
            secondaryComboBoxColumn.DataSource = unfilteredSecondaryBS;
            secondaryComboBoxColumn.DisplayMember = "Name";
            secondaryComboBoxColumn.ValueMember = "ID";

            // this binding source is where I perform my filtered view
            filteredSecondaryBS = new BindingSource();
            DataView dv = new DataView(tblSecondary);
            filteredSecondaryBS.DataSource = dv;
        }
                

       
        private void dataGridView1_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
        {
                if (e.ColumnIndex == secondaryComboBoxColumn.Index)
                {
                    DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)dataGridView1[e.ColumnIndex, e.RowIndex];
                    dgcb.DataSource = filteredSecondaryBS;

                    this.filteredSecondaryBS.Filter = "subid = " +
                        this.dataGridView1[e.ColumnIndex - 1, e.RowIndex].Value.ToString();
                }
            
         }

        private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
        {
           
                if (e.ColumnIndex == this.secondaryComboBoxColumn.Index)
                {
                    DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)dataGridView1[e.ColumnIndex, e.RowIndex];
                    dgcb.DataSource = unfilteredSecondaryBS;

                    this.filteredSecondaryBS.RemoveFilter();
                }
        
        }

SELECT @@rowcount AS 'RowsChanged'