Visual Tree Finder is returning null while searching for Data Grid

Question

I have Tab Control which has many tab items, I am checking Data Grid Items Count while closing tab items. For the first time it works fine(I mean in first iteration). After closing one tab item, in second iteration sellDtg is null. Does anyone know why it is happening? I am concerning that this is UI problem, layout is not being refreshed. Please help me or show direction.

while (tc.HasItems) 
        {
            TabItem ti = tc.SelectedItem as TabItem;
            if (ti.Header == "Продажа") 
            {
                Microsoft.Windows.Controls.DataGrid sellDtg = FindChild<Microsoft.Windows.Controls.DataGrid>(tc, "SellDataGrid");
                if (sellDtg.Items.Count > 0)
                {
                    Sell sl = new Sell();
                    if (Sell.basketfromSellDateListBox == false)
                    {
                        sl.ClearBasket(sellDtg);
                        Sell.ClearFromSellBasket((int)sellDtg.Tag);
                    }
                }
            }
            if (ti != null)
                tc.Items.Remove(ti);

        }

Thanks in advance!!!

Answer 1

I've written a simple FindChildLogical function in analogy for LogicalTreeHelper below:

public static T FindChildLogical<T>(DependencyObject parent, string childName)
           where T : DependencyObject
        {
            if (parent == null) return null;
            var child = LogicalTreeHelper.FindLogicalNode(parent, childName);

            return (T)child;
        }

and you call it as:

Microsoft.Windows.Controls.DataGrid sellDtg = FindChildLogical<Microsoft.Windows.Controls.DataGrid>(ti, "SellDataGrid");

I hope it gets you where you intend to.