Loop asynchronous calls and process data at the end of all runs

Question

I have a method of web service which receives the IP of a server as a parameter and returns a DataSet. Several servers must be consulted by this web service, Um List<string> contains the list of Ips. A loop executes the method, a merge of the return to a local Dataset and then a DataGridView winforms is populated with these data.

The code that does this is simple:

    foreach (var server in servers)
    {
        ds.Merge(ws.GetData(server));
    }

    dataGridView1.DataSource = ds.Tables[0];

This call is run in a queue and takes a while to finish, in addition to locking every form.

How can I convert this process to an asynchronous form using the method GetDataAsync with async and Task to run all calls at once and display the data in the DataGridView at the end?

Answer 1

Do so:

var tasks = servers.Select(server => ws.GetDataAsync(server)).ToArray();
Task.WaitAll(tasks);
var results = tasks.SelectMany(t => t.Result).ToList();
foreach (var res in results)
    ds.Merge(res);

If the method in which the code exists (e.g. a windows Forms control event) can be declared with async, could still use await and let the whole block run after await for when all results are ready:

private async Task EventoDoForm(EventArgs e)
{
    var tasks = servers.Select(server => ws.GetDataAsync(server)).ToArray();
    await Task.WhenAll(tasks);
    var results = tasks.SelectMany(t => t.Result).ToList();
    foreach (var res in results)
        ds.Merge(res);
}

So the event will not crash the form.