Why doesn't it update the ui then run the code wpf

Question

I have this code where I upload some streams to an ftp server. But before that I want to make the spinnerContainer visible. But if I call the method it freezez (It started uploading) and only show the container after it's finished.

spinnerContainer.Visibility = Visibility.Visible;

client.Connect();
client.EmptyDirectory(Id);
client.SetWorkingDirectory(Id);
for (int i = 0; i < streams.Count; i++)
{
    client.UploadStream(streams[i], i.ToString());
}
client.Disconnect();

I want to run the spinnerContainer.Visibility = Visibility.Visible; first then the rest. How can I achieve this?

Answer 1

Your code runs on the UI thread, so until the UI method completes execution, the UI thread will be blocked and the GUI will not update.
Use asynchrony:

private async Task SomeMethod()
{
    spinnerContainer.Visibility = Visibility.Visible;

    await Task.Run(() =>
    {
        client.Connect();
        client.EmptyDirectory(Id);
        client.SetWorkingDirectory(Id);
        for (int i = 0; i < streams.Count; i++)
        {
            client.UploadStream(streams[i], i.ToString());
        }

        client.Disconnect();
    });

}

The call of the method has to be awaited:

await SomeMethod();

In case you are calling it from an event handler, the handler method must be declared async void.