Linq select self reference during creation in C#

Question

Basically what I want is the same that is answered here but in C#: Self-references in object literal declarations

What I have is this code:

private List<myObject> myFunction()
{
    return myList.Select(l => new myObject
    {
        propA = 6,
        propB = 3,
        propC = propA + propB
    }
    ).ToList();
}

Of course it does not work, because I cannot reference propA and propB this way. What it the right way to do it?

Thank you

You can consider to make `propC` calculable: i.e. declare it as `public int propC => propA + propB;` — Sergey Berezovskiy, Jun 06 '17 at 10:42

Roman · Accepted Answer · 2017-06-06T10:46:22.337

6

You can use body in lambda expression:

private List<myObject> myFunction()
{
    return myList.Select(l => 
    {
        var myObject = new myObject
        {
            propA = 6,
            propB = 3        
        };

        myObject.propC = myObject.propA + myObject.propB;

        return myObject;

    }).ToList();
}

Or you can return sum in getter of propC:

public int propC 
{
    get
    {
        return propA + propB;
    }
}

And you don't need to set propC.

edited Jun 06 '17 at 10:46

answered Jun 06 '17 at 10:39

Roman

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You are missing `return myObject;` – Jenish Rabadiya Jun 06 '17 at 10:45

score 3 · Answer 2 · answered Jun 06 '17 at 10:44

If you're not working with Linq to objects, (i.e. the lambdas are required to be expressions, not method delegates as with Linq to SQL/Entity Framework) you could do this with the help of an anonymous object and two Select statements:

return myList
    .Select(l => new {
        propA = 6,
        propB = 3})
    .Select(x => new myObject{
        propA = x.propA,
        propB = x.propB,
        propC = x.propA + x.propB
    })
    .ToList();

Linq select self reference during creation in C#

2 Answers2