Using a partial class property inside LINQ statement

Question

I am trying to figure out the best way to do what I thought would be easy. I have a database model called Line that represents a line in an invoice.

It looks roughly

Answer 1

I think easiest way to resolve this problem is using DelegateDecompiler.EntityFramework (make by Alexander Zaytsev)

It's a library which is able to decompile a delegate or a method body to its lambda representation.

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Explain:

Asume we have a class with a computed property

class Employee
{
    [Computed]
    public string FullName
    {
        get { return FirstName + " " + LastName; }
    }

    public string LastName { get; set; }

    public string FirstName { get; set; }
}

And you are going to query employees by their full names

var employees = (from employee in db.Employees
                 where employee.FullName == "Test User"
                 select employee).Decompile().ToList();

When you call .Decompile method it decompiles your computed properties to their underlying representation and the query will become simmilar to the following query

var employees = (from employee in db.Employees
                 where (employee.FirstName + " " + employee.LastName)  == "Test User"
                 select employee).ToList();

If your class doesn't have a [Computed] attribute, you can use the .Computed() extension method..

var employees = (from employee in db.Employees
                 where employee.FullName.Computed() == "Test User"
                 select employee).ToList();

Also, you can call methods that return a single item (Any, Count, First, Single, etc) as well as other methods in identical way like this:

bool exists = db.Employees.Decompile().Any(employee => employee.FullName == "Test User");

Again, the FullName property will be decompiled:

bool exists = db.Employees.Any(employee => (employee.FirstName + " " + employee.LastName) == "Test User");

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Async Support with EntityFramework

The DelegateDecompiler.EntityFramework package provides DecompileAsync extension method which adds support for EF's Async operations.

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Additionally

You can find 8 way to mix some property values together in EF here:

Computed Properties and Entity Framework. (written by Dave Glick)