Question

为什么我的代码会抛出错误 Cannot perform '=' operation on System.DateTime and System.Int32.，

此行引发错误：

DataRow[] dr = ds.Tables[0].Select("HolidayDate=" +  SelectedDate);

但是当我传递静态日期如“＃2014-10-12＃”然后它可以工作时，我还附加#with selectedDate但程序没有给出响应。

完整代码：

protected void Calndar_SelectionChanged(object sender, EventArgs e)
{

    string SelectedDate = Calndar.SelectedDate.ToString(DateTime.Now.ToString("yyyy") + "-" + "MM-dd");
    DataSet ds = (DataSet)Session["Calendar"];
    DataRow[] dr = ds.Tables[0].Select("HolidayDate=" +  SelectedDate);
    foreach (DataRow drr in dr) 
    {
        Response.Write(SelectedDate);
    }

string SelectedDate存储值，并在response.write中显示

更新的代码也不起作用

protected void Calndar_SelectionChanged(object sender, EventArgs e)
{
    DateTime SelectedDate =new DateTime(DateTime.Now.Year, Calndar.SelectedDate.Month, Calndar.SelectedDate.Day);

    DataSet ds = (DataSet)Session["Calendar"];
    IEnumerable<DataRow> selectedRows = ds.Tables[0].AsEnumerable().Where(row => (row.Field<DateTime>("HolidayDate") == SelectedDate));

    foreach (DataRow drr in selectedRows) 
    {
        Response.Write(drr[4]);
    }
}

Answer 1

如果您想避免此类日期序列化问题，可以使用Linq to DataSet：

DateTime selectedDate = 
  new DateTime(DateTime.Now.Year, Calndar.SelectedDate.Month, Calndar.SelectedDate.Day);
DataSet ds = (DataSet)Session["Calendar"];

IEnumerable<DataRow> selectedRows = ds.Tables[0].AsEnumerable().
  Where(row => (row.Field<DateTime>("HolidayDate") == selectedDate));

foreach (DataRow selectedRow in selectedRows) 
...

为什么我的程序会抛出此错误：无法执行＆＃39; =＆＃39; System.DateTime和System.Int32上的操作

1 个答案: