ActiveDesignerEventArgs.cs

using System.Security.Permissions;

namespace System.ComponentModel.Design
{
    [HostProtection(SecurityAction.LinkDemand, SharedState = true)]
    [PermissionSet(SecurityAction.LinkDemand, Name = "FullTrust")]
    [PermissionSet(SecurityAction.InheritanceDemand, Name = "FullTrust")]
    public class ActiveDesignerEventArgs : EventArgs
    {
        private readonly IDesignerHost oldDesigner;

        private readonly IDesignerHost newDesigner;

        public IDesignerHost OldDesigner => oldDesigner;

        public IDesignerHost NewDesigner => newDesigner;

        public ActiveDesignerEventArgs(IDesignerHost oldDesigner, IDesignerHost newDesigner)
        {
            this.oldDesigner = oldDesigner;
            this.newDesigner = newDesigner;
        }
    }
}