Question

I have 2 tables in SQL:

Table 1  Step Id Step Name  Table 2 Profile Id Step Id Completed 

I would like to return the following results even if there is not match in table 2:

Results Table1.Step Id Table1.Step Name Table2.Profile Id Table2.Completed  

The way I am doing this in SQL is the following:

select * from [Table 1] t1 left join [Table 2] t2 on t1.Step Id = t2.Step Id 

This produces the results I expect.

When I translate this into linq:

public static List<UserCompletion> GetStepCompletion(string category, string profileid) {   List<Step> step = GetSteps(category); List<UserStep> userStep = GetUserSteps(category, profileId);      var q = from s in step          join us in userStep          on s.Id equals us.StepId          select new UserCompletion          {            StepId = s.Id,            Headline = s.StepName,            ProfileId = us.ProfileId            Completed= us.Completed           };       return q.ToList();  } 

It works but like a JOIN not a left join. I only get matching results back.

Also, UserCompletion is an object that I return from this method.

Answer 1

You could also try this (assuming us.Completed is boolean):

var q = from s in step          let us = (from i in userStep where s.Id = i.StepId).SingleOrDefault()          select new UserCompletion          {            StepId = s.Id,            Headline = s.StepName,            ProfileId = us.ProfileId            Completed = us == null ? false : us.Completed           }; 

This won’t turn into a join in sql, but a nested select statement something like this:

select      StepId, Headline, ProfileId,     isnull((select top(1) Completed from userStep where StepId = Id), 0) as Completed from step