C#

public event SoloChangedHandler SoloChanged;             // Your event
public delegate void SoloChangedHandler(Channel sender);      // Your event delegate

private void OnSoloChanged()
{
     if (SoloChanged != null)
          SoloChanged(this);
}

private void chkSolo_Checked(object sender, EventArgs e)
{
     OnSoloChanged();   //Raise your event
}

public bool IsSolo
{
     get { return chkSolo.Checked; }
     set { chkSolo.Checked = value; }
}

private int selectedIndex = -1;
private Channel selectedChannel;

private void ctrlSolo_SoloChanged(Channel sender)
{
     if (sender.IsSolo)
     {
        this.selectedIndex = this.Controls.GetChildIndex(sender);
        this.selectedChannel = sender;
        foreach (Channel channel in this.Controls)
        {
             if (channel != sender)
             {
                 channel.IsSolo = false; //Or you can move this to the Channel control, set it to false whenever mute is true
                 channel.IsMute = true;
             }
        }
     }
     else
     {
        this.selectedIndex = -1;
        this.selectedChannel = null;
        foreach (Channel channel in this.Controls)
        {
            channel.IsSolo = false;
            channel.IsMute = false;
        }
     }
}