Snippet to turn a ListBox into a colored logs renderer

csharp_forms_listbox_logs

public Form1()
{
    InitializeComponent();
    
    // set custom draw method
    List_EventsLog.DrawMode = DrawMode.OwnerDrawVariable;
    List_EventsLog.DrawItem += List_EventsLog_DrawItem;
}

/// <summary>
/// Draw an item in the events list.
/// Implements color based on log level.
/// </summary>
private void List_EventsLog_DrawItem(object sender, DrawItemEventArgs e)
{
    e.DrawBackground();
    if (e.Index == -1) { return; }
    Graphics g = e.Graphics;
    string text = List_EventsLog.Items[e.Index].ToString() ?? "";
    var fontBrush = new SolidBrush(e.ForeColor);
    var selected = (e.State.HasFlag(DrawItemState.Focus) || e.State.HasFlag(DrawItemState.Selected));
    if (text.StartsWith(LogLevels.Notice.ToString()))
    {
        if (selected)
        {
            g.FillRectangle(new SolidBrush(Color.LightGreen), e.Bounds);
            fontBrush = new SolidBrush(Color.Black);
        }
        else
        {
            g.FillRectangle(new SolidBrush(Color.Green), e.Bounds);
            fontBrush = new SolidBrush(Color.White);
        }
    }
    else if (text.StartsWith(LogLevels.Warn.ToString()))
    {
        if (selected) { fontBrush = new SolidBrush(Color.Red); }
        g.FillRectangle(new SolidBrush(Color.Yellow), e.Bounds);
    }
    else if (text.StartsWith(LogLevels.Error.ToString()))
    {
        if (selected) { fontBrush = new SolidBrush(Color.Red); }
        g.FillRectangle(new SolidBrush(Color.Pink), e.Bounds);
    }
    else if (text.StartsWith(LogLevels.Debug.ToString()))
    {
        fontBrush = selected ? new SolidBrush(Color.White) : new SolidBrush(Color.Gray);
    }
    else if (text.StartsWith(LogLevels.Assert.ToString()))
    {
        g.FillRectangle(new SolidBrush(Color.DarkRed), e.Bounds);
        fontBrush = new SolidBrush(Color.White);
    }
    g.DrawString(text, e.Font, fontBrush, new PointF(e.Bounds.X, e.Bounds.Y));
    e.DrawFocusRectangle();
}

/// <summary>
/// Write a message to events log.
/// </summary>
void WriteEventLog(string message, LogLevels logLevel)
{
    // get formatted text
    var msgText = string.Format("{0,-6} | {1,-5} | {2, -16}",
            logLevel.ToString(),
            DateTime.Now.ToShortTimeString(),
            message);

    // add to log list
    if (logLevel != LogLevels.Trace)
    {
        List_EventsLog.Invoke((MethodInvoker)(() =>
        {
            List_EventsLog.Items.Add(msgText);
            if (List_EventsLog.SelectedIndex == List_EventsLog.Items.Count - 2)
            {
                List_EventsLog.SelectedIndex = List_EventsLog.Items.Count - 1;
            }
        }));
    }
}

/// <summary>
/// Log levels for event logs.
/// </summary>
public enum LogLevels
{
    Trace,
    Debug,
    Info,
    Notice,
    Warn,
    Error,
    Assert
}

Usage example:

WriteEventLog("Oh no!", LogLevels.Warn);

Note: works best with monospace font.