Left Join using LAMBDA to get Result in API - asp.net-web-api

Question

How to implement this Join which is in the code below into C# using LAMBDA
Select
VD.Id
, VD.BusinessAddress
, VD.BusinessDesc
, VD.BusinessEmail
, VD.BusinessName
, VD.BusinessZip
, VD.ContactPerson
, VD.ContactNo
, VD.ProfileUrl
, L.Name
, BC.BusinessCategory
from vendorDomain VD WITH(NOLOCK)
left Join Location L WITH(NOLOCK) ON VD.City = L.Id
left join Business_Category BC WITH(NOLOCK) ON VD.BusinessCategory = BC.BusinessId
where VD.IsDeleted = 0
I have to implement the join operation in the following API:
[HttpGet]
public async Task<IActionResult> Get()
{
var VendorList =await _vendorRepository.Query().Where(x => x.IsDeleted == false).ToListAsync();
return Ok(VendorList);
}
There are alot of examples out there but are way to confusing for a novice developer..
EDIT:
This is what I have tried as of now:
var employees = from vndr in context.vendorDomain
join C in context.Location on vndr.City equals C.Id into dep
from dept in dep.DefaultIfEmpty()
select new
{
vndr.BusinessAddress,
vndr.BusinessDesc,
vndr.BusinessEmail,
vndr.BusinessName,
vndr.BusinessWebsite,
vndr.BusinessZip,
vndr.ContactNo,
vndr.ContactPerson,
vndr.Created_At,
vndr.ProfileUrl,
vndr.Url,
dept.Name
};

Answer 1

We will do things first: do the joins and create a view model class that you will return. Because returning anonymous object and using dynamic does get messy.
ViewModel for the joined entities:
public class EmployeesViewModel
{
public string BusinessAddress { get; set; }
public string BusinessDesc { get; set; }
public string BusinessEmail { get; set; }
/* ....all remaining properties */
}
Then we join them properly and select them as an EmployeeViewModel:
var employees = from vndr in context.vendorDomain
join loc in context.Location on vndr.City equals loc.Id
join bus in context.Business_Category on vndr.BusinessCategory = bus.BusinessId
select new EmployeeViewModel
{
BusinessAddress = vndr.BusinessAddress,
BusinessDesc = vndr.BusinessDesc,
BusinessEmail = vndr.BusinessEmail,
/* ... remaining properties here*/
};
Or, if you want the method syntax:
var employees = context.vendorDomain
.Join(context.Location,
vndr => vndr.City,
loc => loc.Id,
(vndr, loc) => new { vndr, loc,})
.Join(context.Business_Category,
vndr_loc.vndr.BusinessCategory,
bus.BusinessId,
(vndr_loc, bus) => new {vndr_loc.vndr, vndr_loc.loc, bus})
.Select(x => new EmployeeViewModel{
BusinessAddress = vndr.BusinessAddress,
BusinessDesc = vndr.BusinessDesc,
BusinessEmail = vndr.BusinessEmail,
/* ... remaining properties here*/
});
As per your comment, you need to print the vendorList after the join. Now that is pretty vague, but I assume you want to submit both to your client / view, so again, we create a ViewModel class for it:
public class EmployeeVendorListViewModel
{
public VendorList VendorList { get; set; }
public EmployeeViewModel Employees { get; set; }
}
The last thing we do is glue it all together in your ActionMethod and return it:
[HttpGet]
public async Task<IActionResult> Get()
{
//renamed using a lower case "v"
var vendorList = await _vendorRepository.Query()
.Where(x => x.IsDeleted == false)
.ToListAsync();
//the join from earlier. You should put it in a repo somewhere, so it does not clutter your controller
var employees = from vndr in context.vendorDomain
join loc in context.Location on vndr.City equals loc.Id
join bus in context.Business_Category on vndr.BusinessCategory = bus.BusinessId
select new EmployeeViewModel
{
BusinessAddress = vndr.BusinessAddress,
BusinessDesc = vndr.BusinessDesc,
BusinessEmail = vndr.BusinessEmail,
/* ... remaining properties here*/
};
//create the final view model and return it
var vm = new EmployeeVendorListViewModel
{
VendorList = vendorList,
Employees = employees
}
return Ok(vm);
}
If you want to use NOLOCK in your query, you have to wrap it in a TransactionScope. This has already been answered here on StackOverflow: NOLOCK with Linq to SQL