{}在lambda表达式中究竟做了什么？

Question

i was going through a code and found following lines of code i was unable to understand...

objDashBoardHierarchyInfo = SubscribeList.GroupBy(x = > new {
    ReportID = x.ReportId, ReportName = x.ReportName, Direction = x.DisplayColumn
})
    .Select(x = > new DashBoardHierarchyInfo {
    ReportID = x.Key.ReportID,
    ReportName = x.Key.ReportName,
    DisplayDirection = x.Key.Direction ? ? 0,
    oListDashBoardReportInfo = x.Select(c = > new DashBoardReportInfo {
        DataSourceObjectName = c.DataSourceObjectName,
        ReportSubType = c.OutputType,
        DataSourceId = c.DataSourceId,
        XvalueFeild = "",
        YvalueFeild = "",
        ReportName = c.ReportName,
        BodyId = c.BodyID,
        ReportID = c.ReportId,
        UserDashboardReportId = c.UserDashboardReportId,
        ChartTypeID = c.ChartTypeID,
        SeriesColor = c.Color,
        SeriesControlTypeId = c.ControlType ? ? 0
    }).ToList < DashBoardReportInfo > ()
}).ToList < DashBoardHierarchyInfo > ();

Answer 1

The new { } create an anonymous type for you and also create object of that anonymous type that is returned. You can read more about anonymous type on this MSDN article .

The statement you are asking about create object of anonymous type using the SubscribeList object being pass through lambda .

new { ReportID = x.ReportId, ReportName = x.ReportName, Direction = x.DisplayColumn }

You can create object of anonymous type without lamda as show under.

var myObj = new {Id=1, Name="abc"};
Console.WriteLine(myObj.Id);
Console.WriteLine(myObj.Name);

Answer 2

new { } syntax creates instance of anonymous type .

new { ReportID = x.ReportId, ReportName = x.ReportName, Direction = x.DisplayColumn }

means that I want to group this list by every possible combination of three properties ReportID , ReportName , DisplayColumn .