2

I have an array of structures. The structure of my structs is this:

    [StructLayout(LayoutKind.Sequential)]
    public struct TOCRRESULTSHEADER
    {
        public int StructId;
        public int XPixelsPerInch;
        public int YPixelsPerInch;
        public int NumItems;
        public float MeanConfidence;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct TOCRRESULTSITEM
    {
        public short StructId;
        public short OCRCha;
        public float Confidence;
        public short X;
        public short Y;
        public short Width;
        public short Height;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct TOCRRESULTS
    {
        public TOCRRESULTSHEADER Hdr;
        public TOCRRESULTSITEM[] Item;
    }

I am populating a structure of type TOCRRESULTS like this:

  TOCRRESULTS MyArray = GetOCRForImage(filename);

I am sorting the array by the Y values just fine using this:

 Array.Sort<TOCRRESULTSITEM>(MyArray.Item, (a,b) => a.Y.CompareTo(b.Y));

Is there a way to sort by Y and X without having to write my own sorting routine?

I tried using LINQ:

 var newarray = OCRLetterArray.Item.OrderBy(x => x.Y).ThenBy(x => x.X).ToArray();

but it never sorted my array.

I apologize for the drastic change from my original posting. I was hoping I could get away with a simple example.

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3
  • Your LINQ example, as written here, won't do anything by design. Commented Nov 20, 2013 at 17:54
  • Edited my answer, should work in your case. Commented Nov 20, 2013 at 19:03
  • Yes it did. I marked it as the answer. THanks! Commented Nov 20, 2013 at 19:07

5 Answers 5

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3

Most efficient would still be to use Array.Sort, avoiding the allocation of a new array:

    Array.Sort(MyArray.Item, (a, b) =>
    {
        var comparison = a.Y.CompareTo(b.Y);
        return comparison == 0 ? a.X.CompareTo(b.X) : comparison;
    });

This will sort by Y then by X. You can easily switch it around to sort by X then by Y if you wish.

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3 Comments

This involves a custom sorting routine, which the question asks not to do. The question doesn't ask about efficiency.
That's not a sorting routine, it's a comparison function exactly like the ones used in the OrderBy/ThenBy examples, only it uses both X and Y. The sorting routine used here is Array.Sort().
To be exact, OrderBy uses a projection function whereas Array.Sort uses a comparison function. Neither is a sort routine.
3

You have to reassign it:

var orderedArray = MyArray.OrderBy(a => a.Y).ThenBy(a => a.X).ToArray();
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4 Comments

Why call ToList? There's nothing here that says a List would be better than an array.
This is not sorting my array at all. I used the code exactly as above.
The actual code is code that I inherited and it signicantly more complex that my original question. I am modifying my original question now...
@Richard No, LINQ doesn't do an in place sort. Instead it will return a new array with the given ordering. If it's important to do an in place sort you could copy it back to the first array.
1

Try this:

MyArray = MyArray.OrderBy(a => a.Y).ToArray();

Calling OrderBy on the array returns a new collection of type IEnumerable<MyStructure>. It doesn't modify the original array. Once you have the new collection, you can call ToArray on it, and reassign it to the original variable.

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1 Comment

How will this help me sort by X and Y?
1

Your LINQ solution looks fine, are you sure you are using it correctly? In contrast to Array.Sort, it is returns the new IEnumerable instead of sorting in-place (as does Array.Sort), so you would have to use

MyArray = MyArray.OrderBy(a => a.Y).ThenBy(a => a.X).ToArray();

You would have to show more code if this does not solve the problem.

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3 Comments

When I use this, I get a "Cannot implicitly convert type 'System.Linq.IOrderedEnumerable<MyArray>' 'MyArray[]' error
@Richard this suggests that your "MyArray" identifier isn't just an array variable - what is it?
I just rewrote the entire original question to better show what I am working with.
1

Yes, implement IComparable

public struct MyStructure: IComparable, IComparable<MyStructure>
 {
      public int X;
      public int Y;

    public int CompareTo(MyStructure other)
    {
        return Y.CompareTo(other.Y);
    }

    public int CompareTo(object obj)
    {
        return CompareTo((MyStructure)obj);
    }
 }
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7 Comments

Isn't this a sorting routine? The question asks how to do it "without having to write my own sorting routine."
In this way you can call Array.Sort<MyStructure>(MyArray) without defining every time the comparison delegate (a,b) => a.Y.CompareTo(b.Y)
I understand that, but it's still a sorting routine.
I don't understand.. you need some kind of routine or algorithm to sort a custom object or structure
@Dan CompareTo() is not a sorting routine, it's a comparison function.
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