C# ToArray() with fixed array size

Question

I have 2D matrix in C# which is built a little complicated. This is the code of matrix generation:

    string[][] learningInputNotCodified = learningDataRaw.Select(ldr => new string[] {
            ldr.ChangeType.ToString(),
            ldr.MutationOperator.Name??"null",
            ldr.MutationOperator.Before??"null",
            ldr.MutationOperator.After??"null",
            ldr.SLOC.ToString(),
            dBContext.TestCases
                .Count(tc => tc.UserMutantPlay.MutantId == ldr.Id).ToString(),
            dBContext.TestCases
                .Where(tc => tc.UserMutantPlay.MutantId == ldr.Id)
                .Select(rtc => new {
                    killCount = dBContext.TestCases
                        .Where(tc => tc.IsMutantKilled
                        && tc.UserMutantPlay.MutantId == ldr.Id
                        && !tc.InputValues.Any(iv =>
                        rtc.InputValues.FirstOrDefault(iv1 => iv1.InputParameterId == iv.InputParameterId).ValueAsString != iv.ValueAsString))
                        .Count()
                }).Sum(tc => tc.killCount).ToString(),
            ldr.OriginalCode.Mutants.Count().ToString(),
            ldr.ASTDiff??"null"
        }.Concat(
            ldr.ParseSubTrees.OrderBy(pst => pst.Height).Select(pst => pst.SerializedTree).ToArray()
            ).ToArray()).ToArray();

Don't worry about the above code. The problem is that I want the matrix to be square. the columns which are hard coded are OK, but those that come from DB ldr.ParseSubTrees.OrderBy(pst => pst.Height).Select(pst => pst.SerializedTree).ToArray() make problem. Before reaching this statement (big statement) I have queried the DB for the max size. So I know the size and just want something like this:

ldr.ParseSubTrees.OrderBy(pst => pst.Height).Select(pst => pst.SerializedTree).ToArray(maxParseTreeDepth)

Although this is example of the thing I need and not the solution but I need to define the array size in a form like this.

And before you suggest solutions, I have to note that Array.Resize won't help. Because it needs a saved object as ref and in a select expression I can't do that.

Federico Dipuma · Accepted Answer · 2017-08-26 13:53:20Z

3

A quick and dirty solution is to concat an array and than use Take():

Before the query:

var paddingArray = new string[maxParseTreeDepth];

Inside query:

ldr.ParseSubTrees
    .OrderBy(pst => pst.Height)
    .Select(pst => pst.SerializedTree)
    .Concat(paddingArray)
    .Take(maxParseTreeDepth)
    .ToArray();

edited Aug 26, 2017 at 13:53

answered Aug 26, 2017 at 13:48

Federico Dipuma

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6 Comments

ConductedClever Over a year ago

:D yes this is really dirty. This will create arrays three/four times! I hold this as the last way. any other Idea???

Federico Dipuma Over a year ago

If you are afraid of multiple array creation, you may always create the array before and then use that instance inside Concat.

D Stanley Over a year ago

@ConductedClever "This will create arrays three/four times!" why do you say that? Only one array will get created in the loop - the one that is generated when you call ToArray.

D Stanley Over a year ago

I would not call this dirty at all. You need to pad arrays that are not big enough, which you do quite effectively.

ConductedClever Over a year ago

Yes, I think you are right. Still not sure enough! But I can accept it for now.

|

Jan Köhler · Accepted Answer · 2017-08-26 13:31:55Z

0

If I understand your question correctly, then you want to get only a certain amount of rows. Maybe taking only x rows is what you're looking for:

ldr.ParseSubTrees
    .OrderBy(pst => pst.Height)
    .Select(pst => pst.SerializedTree)
    .Take(maxParseTreeDepth)
    .ToArray();

answered Aug 26, 2017 at 13:31

Jan Köhler

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1 Comment

ConductedClever Over a year ago

No. As this code shows > Console.WriteLine(arr.Take(4).Count()); > 3 take method just makes a ceiling. But I want to be exactly the length I set.

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