outer join two anonymous types and reference a single property in the join query?

Question

Given:

var memberships = context.Memberships.OrderBy("it.CreateDate").ToList();

            var monthlyCounts = from m in memberships
                                     where m.CreateDate >= today.AddDays(-365) && m.CreateDate <= today
                                     group m by m.CreateDate.Month
                                         into g
                                         select new
                                         {
                                             MemberCount = g.Count(m => m.UserId != null),
                                             MembershipDate = g.Key,
                                         };

I'm trying to join that with a list of months:

 var months = Enumerable.Range(0, (d1.Year - d0.Year) * 12 + (d1.Month - d0.Month + 1))
                .Select(m => new DateTime(d0.Year, d0.Month, 1).AddMonths(m).Month);

This is what I came up with:

var cumlativeCounts = from d in months
                                  join m in monthlyCounts on d equals m.MembershipDate into ms
                                  from m in ms.DefaultIfEmpty()
                                  select new
                                             {
                                                 Month = d,
                                                 Count = m.MemberCount
                                             };

Problem is I get an 'Object Reference not Set to an Instance of an Object' Exception, presumably on m.MemberCount

When I just use Count = m then I get all the properties from the monthlyCounts anonymous type, which is not exactly what I want.

Is there another way to outer join two anonymous types and reference a single property in the join query?

Thanks in advance.

SLaks · Accepted Answer · 2011-11-02 15:00:48Z

1

You can write

m == null ? 0 : m.MemberCount

answered Nov 2, 2011 at 15:00

SLaks

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1 Comment

Rich Over a year ago

that was to easy for you gahhh! >.< I had something similar m.MemberCount != null ? m.MemberCount : 0 of course it did not work =\ Thanks man!

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