C#: Accessing datagridview1 from a backgrounder thread

Question

Im trying to access ui controls on the main thread from a backgroundworker thread. I know this is a well known issue but i cannot find any information on how to access a datagridview in particular from the backgrounder thread. I know the code to make a list box is:

private delegate void AddListBoxItemDelegate(object item);

private void AddListBoxItem(object item)
{
    //Check to see if the control is on another thread
    if (this.listBox1.InvokeRequired)
        this.listBox1.Invoke(new AddListBoxItemDelegate(this.AddListBoxItem), item);
    else
        this.listBox1.Items.Add(item);
}

How does one make datagridview controls work? Also the above method only works for one listbox(listBox1), is there a way to make a method that works for all listbox controls in the main ui?

Thanks

David Hall · Answer 1 · 2011-06-16T14:29:19.310

The Invoke method on the DataGridView works in the same manner as the ListBox.

Below is an example where the DataGridView was originally bound to a BindingList<items> and we create a new list and bind to that. This should be equivalent to your requirement of getting the DataTable from your call to Oracle and setting this as the DataSource.

private delegate void SetDGVValueDelegate(BindingList<Something> items);

void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    // Some call to your data access infrastructure that returns the list of itmes
    // or in your case a datatable goes here, in my code I just create it in memory.
    BindingList<Something> items = new BindingList<Something>();
    items.Add(new Something() { Name = "does" });
    items.Add(new Something() { Name = "this" });
    items.Add(new Something() { Name = "work?" });

    SetDGVValue(BindingList<Something> items)
}

private void SetDGVValue(BindingList<Something> items)
{
    if (dataGridView1.InvokeRequired)
    {
        dataGridView1.Invoke(new SetDGVValueDelegate(SetDGVValue), items);
    }
    else
    {
        dataGridView1.DataSource = items;
    }
}

In my test code that successfully worked with the DataGridView, setting that datasource to the one generated in the DoWork eventhandler.

You can also use the RunWorkerCompleted callback since it is marshalled to the UI thread. An example is below:

backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);

void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    dataGridView1[0, 0].Value = "Will this work?";
}

As for your second part to the question, there are several ways to achieve this. The most obvious is to pass in the ListBox you want to work on when you call the BackGroundWork, like so:

backgroundWorker1.RunWorkerAsync(this.listBox2);

Then you can cast the arguments object within the DoWork eventhandler:

void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    ListBox l = e.Argument as ListBox;

    // And now l is whichever listbox you passed in 
    // be careful to call invoke on it though, since you still have thread issues!               
}

i dont want to use runworkercompleted as my datagrid code is in the middle of backgrounder. my backgrounder thread actually calls another method that wants to output to a datagridview. I dont really understand what you are doing? i want to call a delegate method and pass it the information i want the gridview to display. i dont think your method does that — hWorld, Jun 16 '11 at 13:05
@Dominique - my method updates the datagridview, but there are so many ways of doing that that I can't really give you an example to match what you need without more info. Could you possibly edit your question with the code for method you would have if you weren't working in a background thread? — David Hall, Jun 16 '11 at 13:11
@Dominique - one example of what you could do is use a binding source and call invoke on that instead. — David Hall, Jun 16 '11 at 13:14
In the backgrounder thread, im just reading an oracle database, storing it in a datatable and trying to pass that to defaultgridview method of the datagridview to display it. I need a way to pass the datatable to a datagridview while within the backgrounder thread. — hWorld, Jun 16 '11 at 13:22
@Dominique So all you want to do is update the DataSource? I've changed my example to do this. — David Hall, Jun 16 '11 at 14:20

C#: Accessing datagridview1 from a backgrounder thread

1 Answers1