C# lambda expression question - how to join 2 tables using Lambda statements from the following SQL?

Question

I have 2 tables, and I would like to join them using Lambda statements (not Linq but Lambda).

This is the query that I need:

SELECT
    c.*
FROM
    board as b
LEFT JOIN category as c ON
    b.cid = c.cid
WHERE
    b.bid = 1

How do I do this?

Say if board is a dataset/variable and category is an other dataset/variable then i want somethign like board.Join(category).Where(b=>b.bid==c.cid) ( i know this is wrong but just so you have an idea what i am looking for thank you so much for all your help

Solution 1

If you mean method syntax and not query syntax of linq then you can do

var results = context.boards.Where(b => b.bid == 1)
                            .DefaultIfEmpty()
                            .Join(context.categories, 
                                  b => b.bid,
                                  c => c.cid,
                                  (b, c) => c);

Solution 2

You can use a group join like:

var qry = boards.GroupJoin(
    categories,
    b => b.CategoryID,
    c => c.CategoryID,
    (x, y) => new { Board = x, Categories = y })
    .SelectMany(
    x => x.Categories.DefaultIfEmpty(),
    (x, y) => new { Board = x.Board, Category = y });

Comments

[Chris Eberle]

SQL doesn't have lambda expressions.

[Admin]

i want the C# lambda expression for the following SQL this SQL is just an example all i want to know is how to join 2 datasets using Lambda Expressions

[Saint]

Maybe look at this thread?

[Chris Eberle]

You've given nothing to work with. What have you tried? Give some examples.

[Admin]

why is my post down graded? :(

[Tom H]

possible duplicate of Simple Examples of joining 2 and 3 table using lamda expression

[philiphobgen]

@Kathy - look at @Bala R's answer. It's probably what you want. You may have understood what lamda expressions are. They're only part of the puzzle for you - in your edit above only "b=>b.bid==c.bid" is a lambda, the rest is method syntax.... Take a look at this link: msdn.microsoft.com/en-us/library/bb397947.aspx HTH

[FlyingStreudel]

Why downvote this? Its a valid question, just a dupe. Theres a nifty button you can press to mark it as a dupe that isn't the down arrow.

[FlyingStreudel]

It joins two collections and groups the results, so in this case you would get the group where a board has no corresponding category. msdn.microsoft.com/en-us/library/…