C# Sort Datagridview

Question

I would like to sort my Datagridview at the end of my DownloadFileCompleted event . I tried the following source which is working if it's called on a buttonClick event , but it's not with my DownloadFileCompleted event and I don't understand why.

    // Does work
    private void bt_test_1_Click(object sender, EventArgs e)
    {
        dg_logiciel.Columns[1].SortMode = DataGridViewColumnSortMode.Programmatic;
        dg_logiciel.Sort(dg_logiciel.Columns[1], ListSortDirection.Ascending);
    }

    // Does not work
    void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
    {
        // mycode
        dg_logiciel.Columns[1].SortMode = DataGridViewColumnSortMode.Programmatic;
        dg_logiciel.Sort(dg_logiciel.Columns[1], ListSortDirection.Ascending);
    }

Can someone explain me that?

Answer 1

The reason that dg_logiciel does not get updated is that the the client_DownloadFileCompleted method is being called asynchronously by whatever you're using to download in the background. This means that the the client_DownloadFileCompleted method is being called by a different thread than the one that your datagridview is on. The datagridview is on the UI Thread , and the client_DownloadFileCompleted is being called by some Worker Thread .

To get around this problem you need to send something over to the UI Thread that tells it that it needs to perform some kind of action.

This can be accomplished by calling <control>.Invoke(...) as follows:

dg_logiciel.Invoke((MethodInvoker) delegate(){ dg_logiciel.Sort(dg_logiciel.Columns[1], ListSortDirectionAscending);});

This sends a message over to the UI Thread telling it call the delegate you're passing whenever it gets a chance. In this case the delegate just has one unnamed method inside of it and all that method does is call dg_logiciel.Sort(...); The (MethodInvoker) bit, for the sake of completeness, just casts the delegate as a MethodInvoker type.

A short simple answer can be found here: How does Invoke work underneath?

I hope that helps clear it up at least a little.