LINQ Help

[davetherave2]

Ok you could try something like this then:

This is untested by the way

	 db.SubCategories.GroupBy(subcategory => subcategory.Category.Description).
	   Select(groupedCategory => new 
{
 CategoryDescription =  groupedCategory.Key
, TotalNumberOfProjects =  groupedCategory.Sum(subcategory.ProjectCategories.Any() ? subcategory.ProjectCategories.Count() : 0) 
}  
).ToList()

So we do the grouping first on your category name and then total up the number of projects afterwards.

I haven't used the GroupBy in LINQ too much and if I do it is usually to get something simple. Like a list of strings etc.

Hope this helps. (I'm still picking up LINQ myself)

 

[cotton31]

Works like a charm! Thanks very much!

Your last bit of code was almost what I had, but I was missing the use of Any() and the conditional operator.

Thanks for your help again!

 

[davetherave2]

Not a problem. My development skills must be improving to be able to do this without any sort of development tools.

Glad you got it sorted.

If you have any other issues just give me a shout.

 

[cotton31]

I have another question, which is related!

My whole system revolves around filtering the set of Projects by various properties, so I have a method that applies all the filters and returns a list of Project objects.

This is used in a few places - I want to also use it in what I've been doing above.

As it's a list of Projects, I think I need to Join it to the SubCategories, so I have the following:

db.SubCategories.Join(GetProjects(), subcat => subcat.ProjectCategories.Select(projcat => projcat.ProjectID), proj => proj.ID, (projcat, proj) => new {projcat, proj}).GroupBy(out => out.cs.Category.Description)
                .Select(groupedCat => new
                {
                    CategoryName = groupedCat.Key,
                    NumberOfProjects = groupedCat.Count()
                }
            );

However I'm getting an error:

The type arguments for method 'System.Linq.Enumerable.Join<TOuter,TInner,TKey,TResult>(System.Collections.Generic.IEnumerable<TOuter>, System.Collections.Generic.IEnumerable<TInner>, System.Func<TOuter,TKey>, System.Func<TInner,TKey>, System.Func<TOuter,TInner,TResult>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

This bit subcat.ProjectCategories.Select(projcat => projcat.ProjectID) seems to be causing the error, and I think it's because I'm having go through another entity to get the ID I need (e.g. if I could just do subcat.ProjectID, then it would work fine.)

Am I even on the right track? Any ideas?

Thanks!
Matt