How to convert a multiple conditions like this to lambda

Question

I'm aiming to do a lamba expression with this query, and I'm stuck. I had to do some easy lambdas before and now I need to do a multiple condition mixing or and ands in this one and I'm new with this.

So let me explain a bit of a this structure and you will see why is tricky (at least for a newbie at lambda). I have Requests, where request have many attributes, attributes have name and value, because according to request State they have different attributes in this case RequestState.APPROVAL_PENDING is a constant that will bring the right state and attribute name have being also compared with constants with the attribute names I need and the value need find is wwid in the attribute value.

Then I will make a query.tolist(); and get all the requests, but I need to find out how to lambda this.

var query = from request in DBContext.REQUESTs
                        join attr in DBContext.REQUEST_ATTRIBUTES on request.REQUEST_ID equals attr.REQUEST_ID
                        where (attr.ATTRIBUTE_VALUE == wwid && 
                        (attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_2_WWID || attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_WWID))
                        && request.STATE_ID == RequestState.APPROVAL_PENDING
                        select request;

Have you seen this? What you have is more readable.

Jasen
– Jasen

2017-05-03 02:48:05 +00:00
Commented May 3, 2017 at 2:48 — Jasen
– Jasen, Commented May 3, 2017 at 2:48
@daniel-vega. Did my answer work for you ?

Boney
– Boney

2017-05-13 06:23:53 +00:00
Commented May 13, 2017 at 6:23 — Boney
– Boney, Commented May 13, 2017 at 6:23
@Boney, not really i changed my approach on that time

Daniel Vega
– Daniel Vega

2018-12-01 00:05:32 +00:00
Commented Dec 1, 2018 at 0:05 — Daniel Vega
– Daniel Vega, Commented Dec 1, 2018 at 0:05

Boney · Accepted Answer · 2017-05-03 03:04:45Z

0

var query = DBContext.REQUESTs.Where(request => request.STATE_ID == RequestState.APPROVAL_PENDING)
                        .Join(DBContext.REQUEST_ATTRIBUTES.Where(attr => attr.ATTRIBUTE_VALUE == wwid &&
                                (attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_2_WWID || attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_WWID)),
                            request => request.REQUEST_ID,
                            attr => attr.REQUEST_ID,
                            (request, attr) => request);

answered May 3, 2017 at 3:04

Boney

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Amanvir Mundra · Accepted Answer · 2017-05-03 03:39:42Z

Here's another way of doing this.

Create a navigation property from Request to RequestAttributes:

 public class Request
{
    .... Properties...
    public virtual ICollection<RequestAttribute> RequestAttributes { get; set; }
}
public class RequestAttribute
{
    .... Properties...
    public virtual Request> Request { get; set; }
}

This creates a one to many relationship from Request to RequestAttributes. And your query becomes:

var query = DBContext.REQUESTs.Where(r=> r.REQUEST_ATTRIBUTES.Any(attr=>attr.ATTRIBUTE_VALUE == wwid && 
                    (attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_2_WWID || attr.ATTRIBUTE_NAME == RequestAttributes.APPROVER_WWID))
                    && r.STATE_ID == RequestState.APPROVAL_PENDING)
                    .Select(r=> r);

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