Hide Default Context menu from CefSharp Chromium Web Browser

To hide Default Context menu you need implement IContextMenuHandler.

Add below class into your project

public class MenuHandler : CefSharp.IContextMenuHandler 
{
    public void OnBeforeContextMenu(IWebBrowser browserControl, IBrowser browser, IFrame frame, IContextMenuParams parameters, IMenuModel model)
    {
        model.Clear();
    }

    public bool OnContextMenuCommand(IWebBrowser browserControl, IBrowser browser, IFrame frame, IContextMenuParams parameters, CefMenuCommand commandId, CefEventFlags eventFlags)
    {

        return false;
    }

    public void OnContextMenuDismissed(IWebBrowser browserControl, IBrowser browser, IFrame frame)
    {

    }

    public bool RunContextMenu(IWebBrowser browserControl, IBrowser browser, IFrame frame, IContextMenuParams parameters, IMenuModel model, IRunContextMenuCallback callback)
    {
        return false;
    }
}

Use MenuHandler into browser

ChromiumWebBrowser browser = new ChromiumWebBrowser();
browser.MenuHandler = new MenuHandler();