class Employee
{
[Computed]
public string FullName => 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:
Not every compiled code can be represented as a lambda expression. Some cases are explicitly not supported, other can break and produce unexpected results.
Some of the known cases listed below
Loops
Loops often cannot be represented as an expression tree.
So, the following imperative code would probably throw a StackOverflowException:
var total = 0;
foreach (var item in this.Items) { total += item.TotalPrice; }
return total;
Instead, write it as a declarative Linq expression, which would be supported.
return this.Items.Sum(i => i.TotalPrice);
Recursion and self-referencing
Recursion and self-referencing of computed properties cannot be represented as an Expression tree,
and would probably throw StackOverflowException similarly to loops.
Pattern matching with is ... or ...
is ... or ... pattern matching cannot always be decompiled due to compiler optimizations. The compiler may optimize patterns to use comparison operators, making it impossible to distinguish between genuine comparisons and optimized patterns.
For example:
enum TestEnum { Foo, Bar, Baz }
// This pattern matching:
x is TestEnum.Foo or TestEnum.Bar
// Might compile to:
(uint)x <= 1
Using with EntityFramework and other ORMs
If you are using ORM specific features, like EF's Include, AsNoTracking or NH's Fetch then Decompile method should be called after all ORM specific methods, otherwise it may not work. Ideally use Decompile extension method just before materialization methods such as ToList, ToArray, First, FirstOrDefault, Count, Any, and etc.
