public interface ILogoPlugin
    { 
        string ExecuteAction(string request);   
        string GetApiKey(string request);
        string GetConfig(string request);
        string GetDescription();
        string GetExtension(string request);
        int GetVersion();
        string GetWidgets();
        string OnEvent(string request);
        void SetHost(LogoPluginHost host);
        string ShowWidget(string request);
    }

namespace SampleLogoApp
{
    [ComVisible(true)]
    [Guid("82DB21B7-11E0-4E2A-8907-E78EA....")]
    public class Sample : ILogoPlugin
    {
        [DllImport("user32.dll", SetLastError = true)]
        private static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
        private ILogoPluginHost m_Host;
        public SamplePluginForm1 frm1;
        public SamplePluginForm2 frm2;
      	AppDomain currentDomain = AppDomain.CurrentDomain;

        public Sample()
        {
            ...
        }

        private string Icon_Image()
        {
            return "iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAMAAABg3Am1AAAAhFBMVE.....="; 
        }
        public string ExecuteAction(string request)
        {
            return "{}";
        }
        public string GetApiKey(string request)
        {
            return "{}";
        }
        public string GetConfig(string request)
        {
            return request;
        }
        public string GetDescription()
        {
            return "Sample Logo App ......";
        }
        public string GetExtension(string request)
        {
            return "{}";
        }
        public int GetVersion()
        {
            return 1;
        }
        public string OnEvent(string request)
        {
            return "{}";
        }
        public void SetHost(LogoPluginHost host)
        {
            m_Host = host;
        }
        public string GetWidgets()
        {
            return "["
            + "{"
            + " \"tag\" : 1, "
            + " \"name\" : \"Sample Plugin Widget 1\", "
            + " \"header\" : \"Sample Widget 1\", "
            + " \"description\" : \"" + GetDescription() + "\", "
            + " \"settings\":["
            + " ....}"
            + "]";
        }
        public string ShowWidget(string request)
        {
            return "[...]";
        }
 
    }
}

public int GetVersion()
{
    return 1;
}

public class Sample : ILogoPlugin
{
....
    private ILogoPluginHost m_Host;
	public void SetHost(LogoPluginHost host)
	{
		m_Host = host;
	}
...
}

PluginInfo = new PluginInfo
       {      
           . 
           .
           PluginApiKey ="{\"key\":\"clUa0Wq6rqxkLDJrX2......................z+eIHwA==\"}";   
           .  
           .
       }