SortableBindingList，索引超出范围错误，如何使其线程安全

using System;
using System.Collections.Generic;
using System.ComponentModel;
namespace MyApplication
{
    public class SortableBindingList<T> : BindingList<T>
    {
        private static object syncLock = new object();
        private readonly Dictionary<Type, PropertyComparer<T>> comparers;
        private bool isSorted;
        private ListSortDirection listSortDirection;
        private PropertyDescriptor propertyDescriptor;
        private System.ComponentModel.ISynchronizeInvoke _SyncObject;
        private System.Action<System.ComponentModel.ListChangedEventArgs> _FireEventAction;
        public SortableBindingList()
            : base(new List<T>())
        {
            this.comparers = new Dictionary<Type, PropertyComparer<T>>();
        }
        public SortableBindingList(IEnumerable<T> enumeration, System.ComponentModel.ISynchronizeInvoke syncObject)
            : base(new List<T>(enumeration))
        {
            _SyncObject = syncObject;
            _FireEventAction = FireEvent;
            this.comparers = new Dictionary<Type, PropertyComparer<T>>();
        }
        protected override bool SupportsSortingCore
        {
            get { return true; }
        }
        protected override bool IsSortedCore
        {
            get { return this.isSorted; }
        }
        protected override PropertyDescriptor SortPropertyCore
        {
            get { return this.propertyDescriptor; }
        }
        protected override ListSortDirection SortDirectionCore
        {
            get { return this.listSortDirection; }
        }
        protected override bool SupportsSearchingCore
        {
            get { return true; }
        }
        protected override void InsertItem(int index, T item)
        {
            lock (syncLock)
            {
                base.InsertItem(index, item);
            }
        }
        protected override void ApplySortCore(PropertyDescriptor property, ListSortDirection direction)
        {
            List<T> itemsList = (List<T>)this.Items;
            Type propertyType = property.PropertyType;
            PropertyComparer<T> comparer;
            if (!this.comparers.TryGetValue(propertyType, out comparer))
            {
                comparer = new PropertyComparer<T>(property, direction);
                this.comparers.Add(propertyType, comparer);
            }
            comparer.SetPropertyAndDirection(property, direction);
            itemsList.Sort(comparer);
            this.propertyDescriptor = property;
            this.listSortDirection = direction;
            this.isSorted = true;
            this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
        }
        protected override void RemoveSortCore()
        {
            this.isSorted = false;
            this.propertyDescriptor = base.SortPropertyCore;
            this.listSortDirection = base.SortDirectionCore;
            this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
        }
        protected override int FindCore(PropertyDescriptor property, object key)
        {
            int count = this.Count;
            for (int i = 0; i < count; ++i)
            {
                T element = this[i];
                if (property.GetValue(element).Equals(key))
                {
                    return i;
                }
            }
            return -1;
        }
        protected override void OnListChanged(System.ComponentModel.ListChangedEventArgs args)
        {
            lock (syncLock)
            {
                if (_SyncObject == null)
                {
                    FireEvent(args);
                }
                else
                {
                    _SyncObject.Invoke(_FireEventAction, new object[] { args });
                }
            }
        }
        private void FireEvent(System.ComponentModel.ListChangedEventArgs args)
        {
            base.OnListChanged(args);
        }
    }
}

我得到以下错误：

指数超出范围。必须是非负数并且小于集合的大小。参数名称：index

1. SortableBindingList绑定到DataGridView，虚拟模式
2. 多个线程触发将数据添加到SortableBindingList的事件

private void ProxyScraper_OnProxyFound(Proxy Proxy, int Count)
{       
    ProxyProcessedCount.Text = Count.ToString();
    _ProxyList.Add(Proxy);
}

我试图锁定SortableBindingList，但仍然出现错误，搜索了很多，但找不到解决方案。