wpf datagrid Ienumerable returning null

Question

Using C#.NET4.5, MS Visual Studio 2012, WPF.

Hi guys got some code here that giving me null. This code was a previous solution that I tried. I received no errors but never tested through it since today when I found I debugged there rows were null.

Heres the code:

1st I throw my data I collected from SQL to a datatable and threw it into my datagrid...

 private void LoadPareto(string pg)
 {
     DataTable tbl = new DataTable();
     tbl = mysqlq.SQL_GetPareto(pg);
     paretogrid.ItemsSource = tbl.AsDataView();
     // InsertColumns();
     ShowArrows();
 }

2nd set up binding in XAML...

<DataGrid Name ="paretogrid" ItemsSource="{Binding}"

3rd I created an Ienumerable...

public IEnumerable<System.Windows.Controls.DataGridRow> GetDataGridRow(System.Windows.Controls.DataGrid grid)
{
    var itemsource = grid.ItemsSource as System.Collections.IEnumerable;
    if (null == itemsource) yield return null;
    foreach (var item in itemsource)
    {
        var row = grid.ItemContainerGenerator.ContainerFromItem(item) as DataGridRow; // null?
        if (null != row) yield return row;
    }
}

Then I call it in this method...

private void ShowArrows()
{
    var rows = GetDataGridRow(paretogrid); // fetching null?

    foreach (DataGridRow r in rows)
    {
        DataRowView rv = (DataRowView)r.Item;
        foreach (DataGridColumn column in paretogrid.Columns)
        {
            if (column.GetCellContent(r) is TextBlock)
            {
                TextBlock cellcontent = column.GetCellContent(r) as TextBlock;
                MessageBox.Show(cellcontent.Text);
            }
        }
    }
}

Now the Problem I have is in the Ienumerbale I see my item source contains 12007 records which is perfect. Yet when I step through I find ...

var row = grid.ItemContainerGenerator.ContainerFromItem(item) as DataGridRow;

Is returning null which my "if" statement find it as a false so skips the yield. So of course, when i go to step through the foreach loop in "showarrows" method It doesnt bother since there's null.

So where am I going wrong? am I missing something?

Thanks in advance guys n girls!

Answer 1

Your DataGrid has't yet updated when you're getting the rows. A solution would be to paretogrid.UpdateLayout() right after you set the ItemsSource .

Note, that this is not really good to mix the data and UI code. What you're trying to do could've probably been done in XAML, and you wouldn't have this problem.