Dictionary <string,bool？> error - 修改了集合; 枚举操作可能无法执行

Question

我收到System.InvalidOperationException:收集被修改; 枚举操作可能无法执行.我的以下代码中的错误.

//temporary var for storing column sort orders according to view type
        Dictionary<string, bool?> tempColumnSortOrders=new Dictionary<string,bool?>(4);
 //Check for column name in col list
        if (tempColumnSortOrders.ContainsKey(fieldToSort))
        {
            //If exists set column sort order to new sort order
            //Set new sort order
            tempColumnSortOrders[fieldToSort] = sortOrder;
            var tempSortOrders = tempColumnSortOrders;
            //remove sort order of other columns
            foreach (var kvp in tempSortOrders)
            {
                //Reset other columns sort other than current column sort
                if (kvp.Key != fieldToSort)
                {
                    tempSortOrders[kvp.Key] = null;
                }
            }
            //Return name of column to sort
            return fieldToSort;
        }

堆栈跟踪

[InvalidOperationException:集合已被修改; 枚举操作可能无法执行.]
System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)+52 System.Collections.Generic.Enumerator.MoveNext()+44 GlaziersCenter.Handlers.GetSiteViews.getColumnToSort(Int32 viewType)在d:\ Projects\GlaziersCenter\GlaziersCenter\Handlers\GetSiteViews.ashx.cs:184 GlaziersCenter.Handlers.GetSiteViews.ProcessRequest(HttpContext context)在d:\ Projects\GlaziersCenter\GlaziersCenter\Handlers\GetSiteViews.ashx.cs:68 System.Web.CallHandlerExecutionStep.System.Web .HttpApplication.IExecutionStep.Execute()+ 341 System.Web.HttpApplication.ExecuteStep(IExecutionStep step,Boolean&completedSynchronously)+69

Answer 1

请尝试使用此代码,

List<string> keys = new List<string>(tempSortOrders.Keys);
foreach (var key in keys)
{
    //Reset other columns sort other than current column sort
    if (key != fieldToSort)
    {
        tempSortOrders[key] = null;
    }
}

更新,

将集合转换为列表将解决问题.

Answer 2

foreach循环不允许您迭代的集合的突变.要更改集合,请使用for循环.