C# copy values from array to list

Question

I have following code:

for (int c = 0; c < date_old.Length; c++) 
{
    for (int d = 0; d < date_new.Length; d++)
    {
        newList[c] = data_old[c];

        if (date_old[c] == date_new[d])
        {
            newList[c] = data_new[d];
        }
    }
}

What I'm trying to do is the following:

I have four arrays: date_new, date_old, data_new, data_old and a List called newList. date_old and data_old have the same length and date_new and data_new too. I want to loop through the date arrays check if there are equal date values. While I'm doing this, I want to copy every value from the data_old array to newList. When a value is equal, I want to copy the value at this point from the data_new position into the List. Here I get a OutOfBoundException after the second for loop. What is wrong?

depends on the size of newList – csharpwinphonexaml Nov 07 '14 at 07:10 — csharpwinphonexaml, Nov 07 '14 at 07:10
How about 'newList = data_old.Distinct().ToArray()' – faester Nov 07 '14 at 07:22 — faester, Nov 07 '14 at 07:22

score 2 · Answer 1 · edited Oct 14 '15 at 05:15

2

This exception is thrown when you try to read/write to an array with an index greater than array.Length -1.

Double-check the size of newList.

edited Oct 14 '15 at 05:15

shA.t

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answered Nov 07 '14 at 07:11

Florian Schmidinger

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but Lists have variable size or am I wrong? So when I copy values from an array into a List I don't have to declare the size. I have var newList = new List(); – uzi42tmp Nov 07 '14 at 07:13
can you paste the initialization of your list? – Florian Schmidinger Nov 07 '14 at 07:14
List is variable in length, but you still have to explicitly change the length by adding elements to it. – Peter Duniho Nov 07 '14 at 07:16
try to make an array instead... YourType[] newList = new Yourtype[data_new.Length]() – Florian Schmidinger Nov 07 '14 at 07:17
No it doesn't - he copies the values multiple times because of the two loops – uzi42tmp Nov 07 '14 at 07:59

darcyy · Answer 2 · 2014-11-07T07:24:24.807

2

Make sure your newList is instantiated as

var newList = new DateTime[Math.Max(date_old.Length, date_new.Length)];

Also make sure the length of date_old equals the length of data_old, same thing for date_new and data_new.

Move newList[c] = data_old[c]; to the outer for loop if you can (i.e. to line 3), it's gonna overwrite your new data assigned to newList.

edited Nov 07 '14 at 07:24

answered Nov 07 '14 at 07:18

darcyy

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ok I've noticed that he copies too much values into the array even when I move the line. I just want him to copy every value once. – uzi42tmp Nov 07 '14 at 07:48

score 1 · Answer 3 · answered Nov 07 '14 at 07:24

1

for (int c = 0; c < date_old.Length; c++)
{
     for (int d = 0; d < date_new.Length; d++)
     {
         newList.Add((date_old[c] == date_new[d] ? data_new[d] : data_old[c]));

     }
}

with your list solution and this logic you provided

answered Nov 07 '14 at 07:24

Florian Schmidinger

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C# copy values from array to list

3 Answers3

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