Question

I’m using the following pattern in C#:

IList<foo> x = y.Select(a => new foo {     b = Calc1(),     c = Calc2() }).ToList();  foreach(foo f in x) {     f.d = b / c; } 

What I would like to do though is:

IList<foo> x = y.Select(a => new foo {     b = Calc1(),     c = Calc2()     d = b / c; }).ToList(); 

So the question is: How can you modify this pattern to allow the assignment of a value that is dependent on other values being calculated during the assignment?

(Somebody will probably point out that d should be a property that does the calculation and return a value. This is a contrived example. Assume that the value of d is calculated using other values in addition to c & b which are not available later.)

Answer 1

You can’t re-use initialized properties in an initializer.

I like Erik’s technique. If the query expression syntax is a bother, you can use a full-on anonymous method.

        List<int> y = new List<int>() { 1, 2, 3, 4 };         var x = y.Select(a =>             {                 int b = a + 1;                 int c = a + 2;                 int d = b / c;                 return new { b = b, c = c, d = d };             });