我需要获取DataTable中列的最小DateTime值。 DataTable是从CSV文件动态生成的,因此我直到运行时才知道该列的名称。这里是我得到的代码不起作用...获取最小值 - Min() - DataTable中使用LINQ to DataSets的DateTime列?
private DateTime GetStartDateFromCSV(string inputFile, string date_attr)
{
EnumerableRowCollection<DataRow> table = CsvStreamReader.GetDataTableFromCSV(inputFile, "input", true).AsEnumerable();
DateTime dt = table.Select(record => record.Field<DateTime>(date_attr)).Min();
return dt;
}
为清楚起见,变量表已打破。我基本上需要找到其中一列的DateTime
的最小值(要在运行时选择并由date_attr
表示)。
我已经尝试过几种解决方案(大部分是处理已知列和/或非DateTime字段)。我在运行时抛出一个错误,告诉我它不能执行DateTime转换(这似乎是Linq的问题?)
我已经确认列名称的数据字符串date_attr
是日期值。
UPDATE:堆栈跟踪的要求:
System.InvalidCastException was unhandled by user code
Message="Specified cast is not valid."
Source="System.Data.DataSetExtensions"
StackTrace:
at System.Data.DataRowExtensions.UnboxT`1.ValueField(Object value)
at System.Data.DataRowExtensions.Field[T](DataRow row, String columnName)
at Presenter.Views.NetworkVisualizationDetailPresenter.<>c__DisplayClass1.<GetStartDateFromCSV>b__0(DataRow t) in Presenter\Views\NetworkVisualizationDetailPresenter.cs:line 194
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.Min[TSource](IEnumerable`1 source)
at System.Linq.Enumerable.Min[TSource,TResult](IEnumerable`1 source, Func`2 selector)
atPresenter.Views.NetworkVisualizationDetailPresenter.GetStartDateFromCSV(String inputFile, String date_attr) in Presenter\Views\NetworkVisualizationDetailPresenter.cs:line 194
at Presenter.Views.NetworkVisualizationDetailPresenter.GetDynamicNetworkVisualizationData(String inputFile, Int32 dataMode, Int32 timeInterval, String date_attr, String entity_attr, String event_attr) in Views\NetworkVisualizationDetailPresenter.cs:line 123
at Presenter.Views.NetworkVisualizationDetail.Page_Load(Object sender, EventArgs e) in NetworkVisualizationDetail.aspx.cs:line 114
at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException:
一切我已经看到似乎表明LINQ不喜欢将东西铸造到DateTime? – 2010-04-24 13:38:12