What's wrong here?  This will not show any values unless you uncomment the 2 lines, or uncomment the 2 lines and add more data too get 2 lines of data.

           ObservableCollection<string> FieldValue;
            ObservableCollection<ObservableCollection<string>> tableValues = new ObservableCollection<ObservableCollection<string>>();
            xamDataGrid1.FieldLayoutSettings.AutoGenerateFields = false;

            xamDataGrid1.FieldLayouts.Add(BuildHeader("FirstName", "LastName", "Age"));

            FieldValue = new ObservableCollection<string> { "John", "Doe", "19" };
            tableValues.Add(FieldValue);

            //FieldValue = new ObservableCollection<string>();
            //tableValues.Add(FieldValue);

        private FieldLayout BuildHeader(params string[] headers)
        {
            FieldLayout fldLayout = new FieldLayout();
            for (int i = 0; i < headers.Count(); i++)
            {
                string s = headers[i];
                UnboundField uf = new UnboundField();
                uf.Name = s;
                uf.Label = s;
                uf.BindingPath = new PropertyPath("Items[" + i.ToString() + "]", null);
                fldLayout.Fields.Add(uf);
            }
            return fldLayout;
        }

            xamDataGrid1.DataSource = tableValues;