CODEWITHSUNDEEP
entity-frameworklinq
Rajesh Shetty
Rajesh Shetty

Reputation: 96

How to convert complex query to Model in a LINQ to Entities query

public class Gateway : ModelBase
    {
        public int Id { get; set; }
        public int SystemGroupId { get; set; }
        public string DeviceName { get; set; }
        public string MacAddress { get; set; }
        public bool Enabled { get; set; } 
    }

public class SystemGroup : ModelBase
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

I am joining these two tables.

var Query = (from g in dbContext.Gateways 
join s in dbContext.SystemGroups on g.SystemGroupId equals s.Id
select new {
Id = g.Id,
SystemGroupId = g.SystemGroupId,
SystemGroupName = s.Name,
DeviceName = g.DeviceName,
MacAddress = g.MacAddress,
DeviceType = g.DeviceType,
Enabled = g.Enabled });

and I am sorting these result set using the below code.

if (sortParameter == Resources.ViewResources.Views.SystemGroup)
   Query = Query.OrderBy(x => x.SystemGroupName);
else if (sortParameter == Resources.ViewResources.Views.DeviceName)
   Query = Query.OrderBy(x => x.DeviceName);
else
   Query = Query.OrderBy(x => x.Id);

Till now it is working as expected. Finally, I want to convert it to Gateway.

return Query.Select(x => new Gateway {
 Id= x.Id, 
 SystemGroupId = x.SystemGroupId, 
 DeviceName = x.DeviceName, 
 MacAddress=x.MacAddress, 
 DeviceType= x.DeviceType, 
 Enabled= x.Enabled}).ToList();

While converting to Gateway, it is throwing the error:

The entity or complex type 'Models.Context.Gateway' cannot be constructed in a LINQ to Entities query.

Upvotes: 0

Views: 258

Answers (1)

Ajas Aju
Ajas Aju

Reputation: 745

In Linq-to-Entities you can only project to an anonymous type or a regular class. You can't project to an existing entity type. You can with linq-to-objects like so

return Query.Select new {
Id= x.Id, 
SystemGroupId = x.SystemGroupId, 
DeviceName = x.DeviceName, 
MacAddress=x.MacAddress, 
DeviceType= x.DeviceType, 
Enabled= x.Enabled}).AsEnumerable().Select(x => new Gateway {
        Id= x.Id, 
SystemGroupId = x.SystemGroupId, 
DeviceName = x.DeviceName, 
MacAddress=x.MacAddress, 
DeviceType= x.DeviceType, 
Enabled= x.Enabled}).ToList();

I didnt test this one,Please do comment after try this one.then i can help you to get your answer.

Upvotes: 3

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