How to order by multiple columns using VB.Net lambda expressions

Question

I've done a brief search of this site, and googled this, but can't seem to find a good example. I'm still trying to get my head around the whole "Lambda Expressions" thing.

Can anyone here give me an example ordering by multiple columns using VB.Net and Linq-to-SQL using a lambda expression?

Here is my existing code, which returns an ordered list using a single-column to order the results:

Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder).ToList

Note: The WebCategory object has a child WebPage object (based on a foreign key). I'd like to order by WebPage.DisplayOrder first, then by WebCategory.DisplayOrder.

I tried chaining the order bys, like below, and though it compiled and ran, it didn't seem to return the data in the order I wanted.

Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder).OrderBy(Function(c As WebCategory) c.WebPage.DisplayOrder).ToList

Thanks in advance.

Solution 1

I found this MSDN article in a quick Google search. I guess what your looking for is this:

Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder). _
ThenBy(Function(c As WebCategory) c.WebPage.DisplayOrder).ToList

Solution 2

You should use ThenBy like this:

Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder) _
                               .ThenBy(Function(c As WebCategory) c.WebPage.DisplayOrder) _
                               .ToList()

Comments

[camainc]

Thanks, that's just what I was looking for. What were the Google search terms that you used to find that article, if I might ask?

[camainc]

Thanks! You answered this at the same time as HuBeZa, but since you already have more badges than he does, I gave the answer to him.

[evilspoons]

Wow, I was doing (what I thought was) exactly this and it wouldn't work, I was getting some sort of Linq-related exception... getting incredibly frustrated... then I noticed I forgot the last ".ToList" part. I know it's obvious in retrospect that it needs to be the right data type, but I guess I was having one of those "forest for the trees" moments. Thanks for the information!

[PeterCo]

BTW: If you need your own IComparer, you have to use it twice (once for the .OrderBy and once for the .ThenBy command). Just add , New MyOwnIComparer and of course your code for your class with the name MyOwnIComparer