InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's

InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.

異常代碼如下:

                if (!keyValueFeeCategories.ContainsKey(item.ProjectId + item.Category))
                    keyValueFeeCategories.Add(item.ProjectId + item.Category, item.TotalAmount);