Linq.How to complete this query?

[shapper]

Hello,

I have 3 tables with a many to many relationship:

Professors ProfessorID, Age, ...
Tags TagID, Name, ...
ProfessorsTags ProfessorID, TagID

How can I get all the professors and all tags associated to each
professor using LINQ?

I have the following:

List<ProfessorPaperpapers = (from p in database.Professors
orderby p.Name
select new ProfessorPaper {
Professor = p,
Tags = new List<Tag{

}
}
}).ToList();

ProfessorPaper is a wrapper that contains two properties: Professor
and List<Tag>.
In my query what I am missing is filling the tags for each professor.

Could someone, please, tell me how to do this?

Thanks,
Miguel

[Jon Skeet [C# MVP]]

On Jun 27, 1:15*am, shapper <[e-mail]:

Hello,

I have 3 tables with a many to many relationship:

Professors ProfessorID, Age, ...
Tags TagID, Name, ...
ProfessorsTags ProfessorID, TagID

How can I get all the professors and all tags associated to each
professor using LINQ?

I have the following:

* * * List<ProfessorPaperpapers = (from p in database.Professors
* * * * * * * * * * * * * * * * * * * * * orderby p.Name
* * * * * * * * * * * * * * * * * * * * * select new ProfessorPaper {
* * * * * * * * * * * * * * * * * * * * * * Professor = p,
* * * * * * * * * * * * * * * * * * * * * * Tags = new List<Tag{

* * * * * * * * * * * * * * * * * * * * * * }
* * * * * * * * * * * * * * * * * * * * * }
* * * * * * * * * * * * * * * * * * * * * }).ToList();

ProfessorPaper is a wrapper that contains two properties: Professor
and List<Tag>.
In my query what I am missing is filling the tags for each professor.

Could someone, please, tell me how to do this?

Well, you could try:

Tags = from pt in database.ProfessorsTags where pt.Professor == p
select pt.Tag

I don't know how nicely that will translate into SQL though.

Alternatives will depend on how you've mapped the ProfessorsTags
collection. For instance, if you've got two many-to-one relationships
mapped, and you've made both of them bidirectional, you may be able to
do:

Tags = p.ProfessorsTags.Tags

Again, I don't know offhand what the SQL for this would look like.

Jon

[shapper]

On Jun 27, 6:47*am, "Jon Skeet [C# MVP]" <[e-mail]:

On Jun 27, 1:15*am, shapper <[e-mail]:

Hello,

I have 3 tables with a many to many relationship:

Professors ProfessorID, Age, ...
Tags TagID, Name, ...
ProfessorsTags ProfessorID, TagID

How can I get all the professors and all tags associated to each
professor using LINQ?

I have the following:

* * * List<ProfessorPaperpapers = (from p in database.Professors
* * * * * * * * * * * * * * * * * ** * * orderby p.Name
* * * * * * * * * * * * * * * * * ** * * select new ProfessorPaper {
* * * * * * * * * * * * * * * * * ** * * * Professor = p,
* * * * * * * * * * * * * * * * * ** * * * Tags = new List<Tag{

* * * * * * * * * * * * * * * * * ** * * * }
* * * * * * * * * * * * * * * * * ** * * }
* * * * * * * * * * * * * * * * * ** * * }).ToList();

ProfessorPaper is a wrapper that contains two properties: Professor
and List<Tag>.
In my query what I am missing is filling the tags for each professor.

Could someone, please, tell me how to do this?

Well, you could try:

Tags = from pt in database.ProfessorsTags where pt.Professor == p
select pt.Tag

I don't know how nicely that will translate into SQL though.

Alternatives will depend on how you've mapped the ProfessorsTags
collection. For instance, if you've got two many-to-one relationships
mapped, and you've made both of them bidirectional, you may be able to
do:

Tags = p.ProfessorsTags.Tags

Again, I don't know offhand what the SQL for this would look like.

Jon

Thanks Jon. I will try it