static class Helper
    {
        public static T GetControl<T>(this Control @this, string controlName)where T:Control
        {
            if (@this == null)  throw new ArgumentNullException("source is ass");
            var sourceProperties = @this.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance). Where(a => a.Name.Equals(controlName));
            var fieldInfos = sourceProperties as List<FieldInfo> ?? sourceProperties.ToList(); 
            if (fieldInfos.Any())
              return (T) fieldInfos.First().GetValue(@this);
            return null;
        }
    }

 Button bt = this.GetControl<Button>("Button_1");
            if (bt == null) return;
            bt.BackColor = Color.Yellow;

 public static T GetControl<T>(this Control @this, string nameControl) where T : Control
        {
            if (@this == null || @this.IsDisposed) throw new ObjectDisposedException("source is ass");
            var result = default(T);
            foreach (Control control in @this.Controls)
            {
                if (control is T && string.Equals(nameControl, control.Name))
                {
                    result = control as T;
                    break;
                }
                result = GetControl<T>(control, nameControl);
                if (result != null)
                {
                    break;
                }
            }
            return result;
        }