Complex Linq Query

Question

I need to write a linq that give me max DetailRoot EventDate Where DetailModel Color equals "Red". Review structure below

Dictionary<string, List<DetailRoot>> dataList = Reporter.GetSiteData();

public class DetailRoot
{

public string UserId{ get; set; }
public string Session{ get; set; }

public Datetime EventDate { get; set; }
public IReadOnlyList<DetailModel> DetailList { get; set; }

}

public class DetailModel
{
public string ApplicationGuid { get; set; }
public string ColorType { get; set; }

}

Simone Cappelletti · Answer

You're right my solution would go into exception if it doesn't find the color red. So you can take the other solution from Mario or if you want a default value in case red color is not present you can do something like: var query = from source in dataList.AsEnumerable() let x = source.Value.Any(y => y.DetailList.Any(z => z.ColorType.Equals("Red"))) //where select x ? source.Value.Where(y => y.DetailList.Any(z => z.ColorType.Equals("Red"))).Max(x => x.EventDate) : //some default value; Basically if the check is true you'll get the EventDate property otherwise a default value chosen by you.

David Smith · Answer

As the linq is querying through hundreds of records I get an error Sequence contain no elements how to get pass that error even if that's true. I don't won't that error happening in the middle of that run. Is there away to modify the linq to just return empty or 0 if case is zero

Simone Cappelletti · Answer

Hello, try something like: var query = from source in dataList.AsEnumerable() let x = source.Value.Where(y => y.DetailList.Any(z => z.ColorType.Equals("Red"))).ToArray() //where select x.Max(y => y.EventDate); I saved the list in a variable named x for convenience and that you can reuse in the clause where to add some logic.

Mario Scheeren · Answer

var date = dataList.Where(x => x.DetailList.Any(y => y.ColorType == "Red")).Max(x => x.EventDate);