It sounds like you are blocking the UI thread – i.e. you haven’t released the system to do any painting.
A hacky answer is to inject Application.DoEvents()
into your code – but this is risky, and has problems with re-entrancy etc; and it is just a bit hacky.
A better option may be to do the processing on a BackgroundWorker
, periodically switching to the UI thread to update things (Control.Invoke) – but this may be tricky if you are adding lots of items to a ListView
.
Full example (although you might want to batch the UI updates – not a row at a time):
using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;
class MyForm : Form
{
BackgroundWorker worker;
ListView list;
Button btn;
ProgressBar bar;
public MyForm()
{
Text = "Loader";
worker = new BackgroundWorker();
worker.WorkerReportsProgress = true;
worker.ProgressChanged += worker_ProgressChanged;
worker.DoWork += worker_DoWork;
worker.RunWorkerCompleted += worker_RunWorkerCompleted;
list = new ListView();
list.Dock = DockStyle.Fill;
Controls.Add(list);
btn = new Button();
btn.Text = "Load";
btn.Dock = DockStyle.Bottom;
Controls.Add(btn);
btn.Click += btn_Click;
bar = new ProgressBar();
bar.Dock = DockStyle.Top;
Controls.Add(bar);
}
void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
btn.Enabled = true;
}
void btn_Click(object sender, EventArgs e)
{
worker.RunWorkerAsync();
btn.Enabled = false;
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i < 100; i++)
{
string newRow = "Row " + i.ToString();
worker.ReportProgress(i, newRow);
Thread.Sleep(100);
}
}
void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
list.Items.Add((string)e.UserState);
bar.Value = e.ProgressPercentage;
}
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.Run(new MyForm());
}
}