Using the library with in-memory objects

[pskrtr]

Hi,

I have a model with some calculated fields that must be searched but since they do not exist in the schema naturaly had a System.NotSupportedException: 'The specified type member 'FieldName' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.' thrown at https://github.com/AlexanderKrutov/DataTables.Queryable/blob/80398b19897ee92f7b08eaa48a9a38874425c4b7/DataTables.Queryable/DataTablesQueryable.cs#L84

I am aware of the purpose of this library, the intention is relying on data context.

So my question is, what would be the path to use the library with in-memory objects e.g. List<MyMode> ? My dataset is not too big so it won't hurt. Any tips?

[AlexanderKrutov]

Hi @pskrtr Could you please explain more detailed the problem you trying to solve? It will be good if you share some piece of code with sample data model.

[pskrtr]

Thanks for the reply @AlexanderKrutov, sure.

Here's an example model to demostrate the issue.

public class Person
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    [MaxLength(50)]
    public string Name       { get; set; } 
    [MaxLength(200)]
    public string Description { get; set; }

    public string ReversedName => string.Join("", Name.Reverse());
}

Id, Name and Description are existing in my table. ReversedName on the other hand is a calculated field as you can see. The library has no problem with a default DataTables view, displaying and pagination just works. However when it comes to search something or sort by a column, this calcuated field leads the exception. That's why I'm asking another way to use the library with an in-memory set, e.g.;

public class MyController : ApiController
{
    public JsonResult<object> Get()
    {
        var request = new DataTablesRequest<Person>(Request.RequestUri.Query);
        using (var ctx = new MyContext())
        {
            // fetch all table to filter nor sort in app, not via linq to entities
            var personsInMemory = ctx.Persons.ToList();             

            // this of course does not work
            var persons = personsInMemory.ToPagedList(request); 

            var response = new
            {
                recordsTotal = persons.TotalCount,
                recordsFiltered = persons.TotalCount,
                data = persons
            };
            return new JsonResult ... ;
        }
    }
}

I hope I can explained well.

[AlexanderKrutov]

@pskrtr got it. Try this:

var personsInMemory = ctx.Persons.ToList();                     
var persons = personsInMemory.AsQueryable().AsDataTablesQueryable(request).ToPagedList(request);

[AlexanderKrutov]

@pskrtr hope my previous advice helped to solve your issue, so I'm going to close the case. If no please just reopen it.

[pskrtr]

@AlexanderKrutov It worked flawlessly, thank you so much.