在新对象投影中存储Linq To Entities查询

Question

I have a Linq to Entities query and I want to select some specific columns and store the new object into a pre-defined object. However, I'm getting the error

<object> does not contain a constructor that takes 0 arguments.

Not sure what is wrong here...

Also not sure if this is the best way or if using anonymous type is better instead of creating a payroll object.

Linq Query

public Payroll GetTestCasePayroll(decimal testScenarioID) //not sure if object is correct return
{
    Payroll instance = (from o in DbContext.UI_OnDemandCheckHeader
                        where o.TestScenarioID == testScenarioID
                        select new Payroll(o.PayEntityCode, o.PayrollYear, o.PayrollNumber)).First();
                        //{ PayEntityCode = , PayrollYear = o.PayrollYear, PayrollNumber = o.PayrollNumber }).First();

    return instance;
}

Payroll object

class Payroll
{
    private string _payEntityCode;
    private decimal _payrollYear;
    private string _payrollNumber;

    public Payroll(string payEntityCode, decimal payrollYear, string payrollNumber)
    {
        PayEntityCode = payEntityCode;
        PayrollYear = payrollYear;
        PayrollNumber = payrollNumber;
    }

    public decimal PayrollYear
    {
        get { return _payrollYear; }
        set { _payrollYear = value; }
    }

    public string PayEntityCode
    {
        get { return _payEntityCode; }
        set { _payEntityCode = value; }
    }

    public string PayrollNumber
    {
        get { return _payrollNumber; }
        set { _payrollNumber = value; }
    }

Answer 1

Your Payroll class needs a constructor that takes no parameters eg

Public Payroll() { }

Linq works by creating an empty instance of the output class and then using the setters on each of the properties. It does not use anything but an empty constructor.