Question

So i have fallen into a problem I am able to update values in a data grid when a textbox edits the value of the cell that the datagrid is selected on, this results in a UI update instantly. The pitfal is that i cannot update arbitrary cells that depend on this cell’s value. The data in which the cell/column is bound to changes yet the DataGrid Doesn’t update the depedent cells values. I have a lot of cells so it is very costly to call the DataGrid.Item.Refresh(). I have tried creating a method that just raises an InotifyProperty changed event yet this doesn’t cause an update in the grid. I am at a loss as how to force the GUI to update.

The code for the model cell is below. and the biding code is below it.

public class ModelCell : INotifyPropertyChanged {
    //This is a class that represents a cell that a user clicks on. it contains few items. And should have a reference to the SpreadSheet object
    public String CellName {
        get;
        set;
    }
    public IEnumerable<String> dependents {
        get;
        private set;
    }
    public String Contents {
        get {
            return Host.GetCellContents(CellName);
        }
        set {
            if (value != _contents) {
                IEnumerable<String> tmpDep = Host.SetCellContents(CellName, value);
                try {
                    if (Host.GetCellValue(CellName) is SS.FormulaError) {
                        //Revert the change.
                        Host.SetCellContents(CellName, _contents);
                    } else {
                        _contents = value;
                        NotifyPropertyChanged("Contents");
                        NotifyPropertyChanged("Value");
                        //Next is to notify dependents that we have changed. Since the names will be in the Format of A1
                        this.dependents = tmpDep;
                    }
                } catch (Exception e) {
                    //We got an exception  no change was made to the sheet anyway. 
                    MessageBox.Show(e.Message);
                }
            } else NotifyPropertyChanged("Value");
        }
    }

    public int Row;
    public int Col;
    public override string ToString () {
        return "THis is a test!";
    }


    /// <summary>
    /// Default initialize the empty cell to empty contents. this makes the construction of the objects simpler;
    /// </summary>
    private String _contents = "";

    /// <summary>
    /// This value is contained in the SpreadSheet so it is automatically changed with the Contents.
    /// </summary>
    public String Value {
        get {
            try {
                Object returned = Host.GetCellValue(CellName);
                if (returned is String || returned is Double)
                    return returned.ToString();
                return ((SS.FormulaError)returned).Reason;
            } catch (Exception e) {
                MessageBox.Show("Cell " + this.CellName + " encountered an exception getting the value: " + e.Message);
                return "";
            }
        }
        set {
            //instead assign contents
            NotifyPropertyChanged("Value");
        }
    }
    public SS.Spreadsheet Host {
        set;
        private get;
    }

    /// <summary>
    /// Creates an empty cell with no value or contents with the specified name.
    /// </summary>
    /// <param name="Name">The Name of this cell generally in the format [A-Z][1-99]</param>
    public ModelCell (String Name) {
        this.CellName = Name;
    }
    public ModelCell () {
        //Name will equal the base.ToString()
        this.CellName = base.ToString();
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged (String propertyName) {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (null != handler) {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

public MainWindow () {
        InitializeComponent();
        ViewModel = new MainViewModel();
        DataGrid Sheet = null;
        if (this.FindName("Sheet") is DataGrid)
            Sheet = (DataGrid)this.FindName("Sheet");
        if (Sheet == null)//Exit
            this.Close();
        IValueConverter converter = new ModelCellConverter();
        Binding bind;
        for (int i = 0; i < 26; i++) {
            DataGridColumn col = new DataGridTextColumn();
            col.Header = (char)('A' + i);
            col.IsReadOnly = true;
            col.Width = new DataGridLength(60);
            col.CanUserSort = false;
            //bind = new Binding(new String((char)('A' + i), 1));
            bind = new Binding("indexAbleArr[" + i + "].Value");
            //bind.Converter = new IdentityConverter();
            bind.Mode = BindingMode.OneWay;
            ((DataGridTextColumn)col).Binding = bind;
            Sheet.Columns.Add(col);
        }
        Sheet.ItemsSource = ViewModel.Rows;

        //Current cell display
        Label lab = null;
        if (this.FindName("CurCell") is Label) {
            lab = (Label)this.FindName("CurCell");
            bind = new Binding("ActiveCell.CellName");
            bind.Source = ViewModel;
            bind.NotifyOnSourceUpdated = true;
            lab.SetBinding(Label.ContentProperty, bind);
        } //Don't bind the label if i cant find it
        if (this.FindName("ValueBox") is Label) {
            lab = (Label)this.FindName("ValueBox");
            bind = new Binding("ActiveCell");
            bind.Source = ViewModel;
            bind.Converter = converter;
            bind.NotifyOnSourceUpdated = true;
            lab.SetBinding(Label.ContentProperty, bind);
        }
        TextBox content = null;
        if (this.FindName("Content") is TextBox) {
            content = (TextBox)this.FindName("Content");
            bind = new Binding("ActiveCell.Contents");
            bind.Source = ViewModel;
            bind.Mode = BindingMode.TwoWay;
            bind.NotifyOnSourceUpdated = true;
            content.SetBinding(TextBox.TextProperty, bind);
        }
        ViewModel.ActiveCell = ViewModel.Rows[0].indexAbleArr[0];
 }

I am using XAML To specify the Layout but no binding is done via XAML so nothing noteworthy is in my XAML code. Rows is a Object that contains an array of model cells (indexAbleArray) for the purposes of binding. It also precreates the 26 needed modelcells for the binding to not throw a million null pointer exceptions.

Answer 1

I think the problem is your portion of index based columns indexAbleArr[" + i + "] in the binding Path of your DataGridTextColumns. They are not participating in the property change notifications.

As BalamBalam suggested make that array into an ObservableCollection or you should be raising a property changed notification at row level for property “indexAbleArr” when any cell int that array changes it Value.

Both to me are actually incomplete designs. 🙁