Removing an array from a list of arrays

Question

I have an xml file and want to remove any row from it. For this reason, I assign each row of the xml file to a list:

List<string[]> lines = new List<string[]>();
List<string> clmns = new List<string>();//each row is written to clmns
...
lines.Add(clmns.ToArray());

As you may expect, lines list will be like

{ "1", "2", ... },
{ "4", "5", ... },
...

Assume that I want to delete the row (the array in lines) holding "5". How can I make it?

I thought I can delete the array by using lines.RemoveAt(1). But, I couldn't find a way to find the index of array holding the search string.

BradleyDotNET · Accepted Answer · 2014-04-16 19:12:37Z

5

You are awfully close. An array is just an object, so the following will work:

lines.Remove(lines.First(a => a.Contains("5")));

This gets the first array in the collection with a "5" and returns the array object to Remove which then removes it.

To remove all of them:

lines.RemoveAll(a => a.Contains("5"));

answered Apr 16, 2014 at 19:12

BradleyDotNET

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6 Comments

Siha Over a year ago

That's great! It works. Thank you! Should I study LINQ to learn such statements?

user2819245 Over a year ago

@Siha: FYI: lines.First will throw an exception if no line with a "5" is found. If this is not desired, use lines.FirstOrDefault instead and check its result before passing it to lines.Remove

Siha Over a year ago

A valuable comment. Thank you.

BradleyDotNET Over a year ago

Thanks for the FirstOrDefault comment, that can bite you pretty hard :). As far as learning LINQ, yes and no. I used a LINQ extension method, and passed it a lambda expression. Learning about those will take you a different route than learning about LINQ itself (since it is basically a language unto itself, similar to SQL). In the end, learning both will be of great benefit though!

BradleyDotNET Over a year ago

@Siha, as an aside (if you do start studying LINQ) the example I gave uses LINQ-To-Objects. The syntax is the same for all versions of LINQ, but they are separate things. For general use, the extensions are enough :)

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Sriram Sakthivel · Accepted Answer · 2014-04-16 19:14:40Z

3

List.FindIndex method can help you here.

int index = lines.FindIndex(x=> x.Contains("5"));
if(index >= 0)
{
   lines.RemoveAt(index);
}

answered Apr 16, 2014 at 19:14

Sriram Sakthivel

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1 Comment

Siha Over a year ago

Thank you. This is also a useful one!

123 456 789 0 · Accepted Answer · 2014-04-16 19:28:06Z

1

You need to loop to the array list and remove it manually. Assuming you just want to delete the first "5".

foreach(var line in lines)
{
 if(line.Contains("5"))
 {
  lines.Remove(line);
  break;
 }
}

edited Apr 16, 2014 at 19:28

answered Apr 16, 2014 at 19:13

123 456 789 0

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4 Comments

itsme86 Over a year ago

This will throw an exception because you're modifying the foreach enumerable within the loop.

123 456 789 0 Over a year ago

@itsme86 No it won't. It will if I iterate one more time.

BradleyDotNET Over a year ago

Interestingly enough, it won't break if you iterate backwards. Besides that, I'm not sure what this gains you over using .First, .FirstOrDefault, or something like that.

123 456 789 0 Over a year ago

Showing how to do it without using LINQ. Especially for people who are new to C# who hasn't tackled LINQ.

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