how to convert T-SQL Query to linq

Question

i have 4 table in SQL: DocumentType,ClearanceDocument,Request, RequestDocument.
i want when page load and user select one request, show all Document Based on clearanceType in RequestTable and check in RequestDocument and when exist set is_exist=true

I have written this query with SqlServer Query Editor for get result this Scenario but i can't convert this Query to Linq

    select *,
    is_Orginal=
    (select is_orginal from CLEARANCE_REQUEST_DOCUMENT 
    where 
    DOCUMENT_ID=a.DOCUMENT_ID and REQUEST_ID=3)
    from 
    DOCUMENT_TYPES a
    where 
    DOCUMENT_ID in 
    (select DOCUMENT_ID from CLEARANCE_DOCUMENTS dt 
    where 
    dt.CLEARANCE_ID=
    (SELECT R.CLEARANCE_TYPE FROM CLEARANCE_REQUEST R 
    WHERE 
    R.REQUEST_ID=3)) 

i write this Query in linq but not work

 var list = (from r in context.CLEARANCE_REQUEST
                        where r.REQUEST_ID == 3
                        join cd in context.CLEARANCE_DOCUMENTS on r.CLEARANCE_TYPE equals cd.CLEARANCE_ID
                        join dt in context.DOCUMENT_TYPES on cd.DOCUMENT_ID equals dt.DOCUMENT_ID into outer
                        from t in outer.DefaultIfEmpty()
                        select new
                                   {
                                        r.REQUEST_ID,
                                        cd.CLEARANCE_ID,
                                        t.DOCUMENT_ID,
                                        t.DOCUMENT_NAME,
                                        is_set=(from b in context.CLEARANCE_REQUEST_DOCUMENT where 
                                                    b.REQUEST_ID==r.REQUEST_ID && b.DOCUMENT_ID==t.DOCUMENT_ID
                                                    select new{b.IS_ORGINAL})
                                   }

                       ).ToList();

I want convert this Query to LINQ. Please help me. Thanks.

Answer 1

Since your query won't be executed untill you iterate over the data, you can split your query in several subqueries to help you obtain the results like this:

var clearanceIds = context.CLEARANCE_REQUEST
                          .Where(r => r.REQUEST_ID == 3)
                          .Select(r => r.CLEARANCE_TYPE);
var documentIds = context.CLEARANCE_DOCUMENTS
                         .Where(dt => clearanceIds.Contains(dt.CLEARANCE_ID))
                         .Select(dt => dt.DOCUMENT_ID);
var result = context.DOCUMENT_TYPES
                    .Where(a => documentIds.Contains(a.DOCUMENT_ID))
                    .Select(a => new
                    {
                        // Populate properties here
                        IsOriginal = context.CLEARANCE_REQUEST_DOCUMENT
                                            .Single(item => item.DOCUMENT_ID == a.DOCUMENT_ID &&
                                                              item.REQUEST_ID == 3)
                                            .IS_ORIGINAL
                    })
                    .ToList();

Answer 2

There is no need to manually join objects returned from an Entity Framework context.

See Why use LINQ Join on a simple one-many relationship?

If you use the framework as intended your job will be much easier.

var result = var clearanceTypes = context.CLEARANCE_REQUEST
    .Single(r => r.REQUEST_ID == 3)
    .CLEARANCE_DOCUMENTS
    .SelectMany(dt => dt.DOCUMENT_TYPES)
    .Select(a => new 
    {
        DocumentType = a,
        IsOriginal = a.CLEARANCE_REQUEST_DOCUMENT.is_original
    });