Datagridview column only shows its cell values on physical click

See more:

C#

forms

I have a method called Search(), its task is to retrieve many purchase orders and show them in a datagridview as a BindingList but adding an additional column manually. The problem is that everything works correctly when I physically press the search button however when I call the method on the form load event it will work except that the extra column that I added manually does not show its cell values, it will only show them after I click the button.

private void Search()
        {
            dgvResults.DataSource = null;
            List<PurchaseOrder> pos = new List<PurchaseOrder>();

            // Check if search criteria is valid
            bool searchCriteriaOk = false;
            if (rdoById.Checked && txtSearch.Text.Length == 8)
            {
                pos = service.GetPurchaseOrders(1, LoginData.EmployeeId, Convert.ToInt32(txtSearch.Text), DateTime.Today, DateTime.Today, null);
                searchCriteriaOk = true;
            }
            else if (rdoById.Checked && txtSearch.Text.Length != 8)
            {
                MessageBox.Show("The purchase order id must be 8 digits long");
            }
            else if (rdoByDate.Checked && dtpStart.Value < dtpEnd.Value)
            {
                POStatus? status = null;
                if (rdoPending.Checked)
                {
                    status = POStatus.Pending;
                }
                if (rdoClosed.Checked)
                {
                    status = POStatus.Closed;
                }
                pos = service.GetPurchaseOrders(2, LoginData.EmployeeId, 0, dtpStart.Value, dtpEnd.Value, status);
                searchCriteriaOk = true;
            }
            else if (rdoByDate.Checked && !(dtpStart.Value < dtpEnd.Value))
            {
                MessageBox.Show("Start date must be less than end date");
            }

            if (searchCriteriaOk)
            {
                if (pos.Count > 0)
                {
                    if (LoginData.EmployeeType == EmployeeType.RegularEmployee || LoginData.EmployeeType == EmployeeType.HREmployee)
                    {
                        foreach (var po in pos.ToList())
                        {
                            if (po.EmployeeId != LoginData.EmployeeId)
                            {
                                pos.Remove(po);
                            }
                        }
                    }

                    dgvResults.DataSource = new BindingList<PurchaseOrder>(pos);
                    dgvResults.Columns["TotalAfterTax"].DefaultCellStyle.Format = "c2";
                    foreach (DataGridViewColumn column in dgvResults.Columns)
                    {
                        if (column.Name != "PurchaseOrderId" && column.Name != "CreationDate" && column.Name != "TotalAfterTax")
                        {
                            column.Visible = false;
                        }

                        if (column.Name == "PurchaseOrderId")
                        {
                            column.HeaderText = "PO Number";
                        }

                        if (column.Name == "CreationDate")
                        {
                            column.HeaderText = "Date";
                        }

                        if (column.Name == "TotalAfterTax")
                        {
                            column.HeaderText = "Total";
                        }
                    }

                    if (dgvResults.Columns["PoItems"] != null)
                    {
                        dgvResults.Columns.Remove("PoItems");
                    }

                    dgvResults.Columns.Add("PoItems", "Items");
                    foreach (DataGridViewRow row in dgvResults.Rows)
                    {
                        string itemToAddToDgv = "";
                        int poId = Convert.ToInt32(row.Cells["PurchaseOrderId"].Value);
                        foreach (PurchaseOrder purchaseOrder in pos.ToList())
                        {
                            if (purchaseOrder.PurchaseOrderId == poId)
                            {
                                foreach (Item item in purchaseOrder.Items.ToList())
                                {
                                    itemToAddToDgv += " *" + item.Name;
                                }
                            }
                        }
                        row.Cells["PoItems"].Value = itemToAddToDgv;
                    }

                    dgvResults.Rows[0].Selected = true;
                }
                else
                {
                    MessageBox.Show("No Purchase Orders found");
                }
            }
        }

What I have tried:

I have even tried to call the .PerformClick() method on the form load but it won't work