从其他线程更新wpf datagrid单元

Question

I'm trying to implement a simple spreadsheet using WPF datagrid. When users input a formula in a cell, engine calculates the formula and update the cell with the calculated value. But most of calculations i handle take long time, so i want to calculate those in other threads.

I tried to implement this using CellEditEnding event like below. (the ItemsSource of dataGrid1 is bound to the DataTable dtab.)

private void dataGrid1_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e) {
    Action calc = () => {
        int r = dataGrid1.Items.IndexOf(e.Row.Item);
        int c = dataGrid1.Columns.IndexOf(e.Column);
        dtab.Rows[r].SetField(c, "X"); // a calculated value
    };            
    Action update = () => {
        if (dataGrid1.Dispatcher.CheckAccess()) calc();
        else dataGrid1.Dispatcher.BeginInvoke(calc);
    };

    //update(); // run from the same ui thread
    Task.Factory.StartNew(update); // run from a different thread
}

When it update the cell value from the same UI thread, cell is updated with value "X", but from the different thread, it is not. How can i update the cell with value "X" from a different thread?

EDIT: My code does not throw any InvalidOperationException bcz i used the Dispatcher.BeginInvoke(). My problem seems that the user input value (formula) overwrites the calculated value which i want to display.

Answer 1

You cannot update the GUI from another thread. Fortunately .Net provides a mechanism to handle this:

uiControl.**Dispatcher**.Invoke(delegate)

For example

dataGrid1.Dispatcher.Invoke(() => MyUpdateFunction(dataGrid1, data))

Edit: Sorry the original code was for Windows.Forms

Answer 2

Using dispatcher is not a good idea. It can render your UI non responsive if not coded properly. If you plan to use datagrid in multithreaded setup then you should use events to reflect the updates. I would recommend a combination of ObservableCollection with INotifyPropertyChanged as better alternative. I have published a template here :

http://www.codeproject.com/Articles/1086714/A-Template-For-Using-Datagrid-in-Monitoring-UI

Answer 3

Take a look at the WPF Dispatcher Class . You have quite a few options to perform threaded tasks from the Dispatcher. Review the BeginInvoke and Invoke methods.