LINQ Replacement for Nested Array Iteration and Update?

Question

I need some help with syntactic sugar. I have a ThisClass[3] and ThatClass[3].

public class ThisClass
{
    public string Thing1;
    public string Thing2;
    public string Thing3;
    public string Thing4;
}

public class ThatClass
{
    public string Thing1;
    public string Thing2;
}

Each instance in the array of ThatClass was created based on an instance in the same position of array ThisClass. So ThatClass[0] has its fields with the same values as ThisClass[0], except it only has 2 fields instead of 4.

I would like to now update each instance in the ThisClass array, with fields from the matching index position of the object in the ThatClass array. I could do nested for loops, but I need help thinking through a LINQ option.

 ThisClass[0].Thing1 = ThatClass[0].Thing1; 
 ThisClass[0].Thing2 =  ThatClass[0].Thing2;

works but I am sure could be done better. Using C#, .NET 4.5.

Jon Skeet · Accepted Answer · 2013-05-17 20:15:11Z

7

I don't see any need for nested loops:

for (int i = 0; i < theseClasses.Length; i++)
{
    theseClasses[i].Thing1 = thoseClasses[i].Thing1;
    theseClasses[i].Thing2 = thoseClasses[i].Thing2;
}

You could potentially add a CopyFrom(ThatClass) method to ThisClass, leading to:

for (int i = 0; i < theseClasses.Length; i++)
{
    theseClasses[i].CopyFrom(thoseClasses[i]);
}

... but that's all I'd do. LINQ is do to with querying, not causing side-effects... I don't think it's a good fit here.

answered May 17, 2013 at 20:15

Jon Skeet

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Comments

Kaveh Shahbazian · Accepted Answer · 2013-05-17 21:06:03Z

1

Attention: As @Jon put, LINQ is not about causing side-effects and if you do so you may end up with a code with unexpected behavior (but it's possible).

This code does that:

ThisClass[] these = new ThisClass[100];
ThatClass[] those = new ThatClass[100];

// init these and those items

those.Zip(these, (that, @this) =>
{
    @this.Thing1 = that.Thing1;
    @this.Thing2 = that.Thing2;
    return that;
}).ToList();

answered May 17, 2013 at 21:06

Kaveh Shahbazian

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Comments

It'sNotALie. · Accepted Answer · 2013-05-17 21:19:33Z

-1

As you're asking for LINQ... this will get you an unrelated IEnumerable<ThisClass>, and will not modify the original array. (I'm assuming that the thisClass and thatClass arrays are called thisArray and thatArray, respectively)

thisArray.Select((n, x) => { n.Thing1 = thatArray[x].Thing1; n.Thing2 = thatArray[x].Thing2; return n; }).ToArray();

(If you really wanted LINQ and assigning it, just assign it back to the original array)

edited May 17, 2013 at 21:19

answered May 17, 2013 at 20:25

It'sNotALie.

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3 Comments

It'sNotALie. Over a year ago

@Downvoter, What. Is. The. Problem? He asked for LINQ, I gave LINQ. I DID mention it would not modify the original one, and it DOES work. I've tested it. What is the problem?

svick Over a year ago

Your code won't work, because Select() is lazy. So, if you do this, nothing will actually happen. That's one reason why using LINQ to do this is a bad idea.

It'sNotALie. Over a year ago

@svick Fixed that, my overlook.

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