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.NET Forum / Languages / C# / April 2008complex List<> sorting
I have an Interface InterfaceBase, and two classes Type 1 and Type 2 that implements InterfaceBase Class Type1 has a string property Title Class Type2 has a string property Title and an int property Ordering List<BaseC> list I would like to sort the list by the value of Ordering (Type 1's Ordering is always 0) and a secondary order by the string property Title alphabetically. I tried writing my own Comparision code, it doesn't seem to work Thanks for your help Tem I would like to know how to write this in LINQ >I have an Interface InterfaceBase, and two classes Type 1 and Type 2 that >implements InterfaceBase [quoted text clipped - 13 lines] > > Tem > I would like to know how to write this in LINQ You don't need LINQ for this; you can sort the existing list using a Comparer<T>: List<InterfaceBase> list = new List<InterfaceBase>(); list.Sort((x, y) => { int result = x.Ordering.CompareTo(y.Ordering); if (result == 0) result = string.Compare(x.Title, y.Title); return result; }); or in C# 2 (VS2005): list.Sort(delegate (InterfaceBase x, InterfaceBase y) { int result = x.Ordering.CompareTo(y.Ordering); if (result == 0) result = string.Compare(x.Title, y.Title); return result; }); If you really want to use LINQ, you can - but note that you get a new list - you don't sort the existing one: List<InterfaceBase> newList = ( from item in list orderby item.Ordering, item.Title select item).ToList(); Marc >I have an Interface InterfaceBase, and two classes Type 1 and Type 2 that >implements InterfaceBase > >Class Type1 has a string property Title >Class Type2 has a string property Title and an int property Ordering I assume neither property is part of the interface? >List<BaseC> list What is BaseC as opposed to InterfaceBase? >I would like to sort the list by the value of Ordering (Type 1's Ordering is >always 0) and a secondary order by the string property Title alphabetically. > >I tried writing my own Comparision code, it doesn't seem to work Could you post some actual code - or maybe a simplified, but compileable version of what you are trying to do - it is hard to help without knowing the details or seeing what you tried that didn't work. Regards, Gilles. Sorry it's a typo it's supposed to be List<InterfaceBase> list >>I have an Interface InterfaceBase, and two classes Type 1 and Type 2 that >>implements InterfaceBase [quoted text clipped - 21 lines] > Regards, > Gilles. > [...] > I would like to sort the list by the value of Ordering (Type 1's > Ordering is always 0) and a secondary order by the string property Title > alphabetically. > > I tried writing my own Comparision code, it doesn't seem to work As Gilles suggests, It would be better if you can show what you've already tried. That has two benefits: first, we can see what particular approach to comparing and sorting you're trying; second, we can provide an answer that more closely fits what you've done already, rather than sending you down some entirely different-but-equivalent path. The general answer is that you'll need to either create a new interface that can be used for sorting that encapsulates the properties you want to sort on (Type1 would always return 0 for the Ordering, of course), or you need a comparer that understands that you're dealing with two different classes, checks the actual type of each object and compares them appropriately. In the former paradigm, you can simply make the new interface inherit IComparable and have each class implement their own Compare() method. In the latter paradigm, you'll probably be writing a standalone IComparer that does the work, though you could in fact have each class implement IComparable<BaseC> and do that work. You mention in a second post that you want to do this in LINQ, but I'm not sure that really has much to do with this. The hard part is unifying your types so that they are comparable, and that's going to be pretty much the same with or without LINQ, I think. Pete I've decided to use another method to store the data. Thank you guys for your help. >I have an Interface InterfaceBase, and two classes Type 1 and Type 2 that >implements InterfaceBase [quoted text clipped - 13 lines] > > Tem Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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