How to call Expression Func with two input parameters - linq

Question

I have following Expression Func which is receiving two input paramters, first is Person Object, second is bool and returning another type of Object PersonProfile
private Exression<Func<Person, bool, PersonProfile>> PersonProfileProjection => (person, isValid) =>
new PersonProfile
{
FirstName = person.FirstName,
HasAddress = isValid ? person.Address1 : null
};
And I am trying to call this while fetching Person table from dbContext.
_dbContext.Persons.Select(PersonProfileProjection);
I am confused how to send boolean parameter inside PersonProfileProjection. It works when I only put one input and one output parameter like this. But I want extra boolean input as well.
Any help would be highly appreciated.

Answer 1

You can follow Microsoft documentation for this : Expression Class
One sample created for SQLite that show above function usage.
public void GetData()
{
var connection = new SQLiteConnection(#"Data Source=database.sqlite;Version=3;");
var context = new DataContext(connection);
connection.Open();
var createtableQuery = #"
drop table Company;
CREATE TABLE[Company]
(
[ID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
[Seats] INTEGER NOT NULL
);
";
var command = new SQLiteCommand(createtableQuery, connection);
command.ExecuteNonQuery();
Company com = new Company()
{
Id = 6,
Seats = 7
};
context.GetTable<Company>().InsertOnSubmit(com);
context.SubmitChanges();
var companies = context.GetTable<Company>();
foreach (var company in companies)
{
Console.WriteLine("Company: {0} {1}",
company.Id, company.Seats);
}
//compile Expression using Compile method to invoke it as Delegate
Func<int,int, Company> PersonProfileProjectionComp = PersonProfileProjection.Compile();
var dd = companies.Select(p => PersonProfileProjectionComp(p.Id,p.Seats));
//// Below line inline use. Both works.
//var dd = companies.Select(p => PersonProfileProjection.Compile().Invoke(p.Id,p.Seats));
}
private System.Linq.Expressions.Expression<Func<int, int, Company>> PersonProfileProjection => (person, seats) =>
new Company
{
Id = person,
Seats = seats
};
or in one line use this :
PersonProfileProjection.Compile().Invoke(person, isValid)

Answer 2

You could declare it as a Func instead of an expression:
private Func<Person, bool, PersonProfile> PersonProfileProjection => (person, isValid) =>
new PersonProfile
{
FirstName = person.FirstName,
HasAddress = isValid // do what you meant to do
};
... and call it as:
_dbContext.Persons.Select(p => PersonProfileProjection(p, true));
You could as well write an ordinary method:
private PersonProfile PersonProfileProjection(Person person, bool isValid)
{
return new PersonProfile
{
FirstName = person.FirstName,
HasAddress = isValid // do what you want to do
};
}
...and call it the same way:
_dbContext.Persons.Select(p => PersonProfileProjection(p, true));