Exclude last element in a loop

Question

I have a loop in my app. Code is following :-

foreach (DataRow dr in dt.Rows)
    ColorNames +=dr["ColorName"].ToString() + "\n";

But i don't want to add \n at the last Datarow. Any suggestion how to do it?

possible duplicate of [Identifying last loop when using for each](http://stackoverflow.com/questions/1068110/identifying-last-loop-when-using-for-each) — Henk Holterman, May 10 '12 at 11:13

Sergey Berezovskiy · Answer 1 · 2012-05-10T11:08:25.810

8

ColorNames = String.Join("\n", dt.Rows.Select(dr => dr["ColorName"].ToString()));

Here is updated version (forgot that cast to Enumerable needed):

ColorNames = String.Join("\n", dt.AsEnumerable().Select(dr => dr.Field<string>("ColorName")));

edited May 10 '12 at 11:08

answered May 10 '12 at 11:00

Sergey Berezovskiy

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+1, but: you need `+=` instead of `=` to mimic the original code behaviour. – Vlad May 10 '12 at 11:04
For reference, in .NET 4 onwards you can pass in an IEnumerable, so you don't need the overhead of creating an array. – SimonC May 10 '12 at 11:04
@Vlad: You don't. You assign the result of String.Join to ColorNames. – VVS May 10 '12 at 11:05
@VVS: Not quite. Imagine that `ColorNames` was non-empty before the beginning of the code. – Vlad May 10 '12 at 11:06
@Vlad if it was not empty, then you are right `+=` should be used. But I think assignment is what he needs – Sergey Berezovskiy May 10 '12 at 11:10

Nikhil Agrawal · Accepted Answer · 2012-05-10T13:01:08.513

2

Foreach do not work on index.

Option 1: ForEach Loop

Use foreach loop. Loop till last and outside loop do like

ColorNames.Substring(0, ColorNames.Length-1);

Option 2: For Loop

Use for loop and check for index inside loop for all indexes till last. add \n and in last index do not add \n

for (int i = 0; i < dt.Rows.Count; i++)
{
   ColorNames += i < dt.Rows.Count-1 
           ? dr["ColorName"].ToString() + "\n"
           : dr["ColorName"].ToString();
}

OR

for (int i = 0; i < dt.Rows.Count; i++)
   ColorNames += dr["ColorName"].ToString() + (i < dt.Rows.Count-1 ?  "\n": "");

Option 3: LINQ

ColorNames = String.Join("\n", dt.Rows.Select(dr => dr["ColorName"].ToString()));

edited May 10 '12 at 13:01

answered May 10 '12 at 10:59

Nikhil Agrawal

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1

Option 3 copy & pasted from lazyberezovsky's answer? – VVS May 10 '12 at 11:07
@Nikhil, Option 2 seems great. – s.k.paul May 10 '12 at 11:15
@No. I copied & pasted it from my brain. Its common practice that `DataRow` variable is taken as `dr` just as `DataTable` variable is taken as `dt`. – Nikhil Agrawal May 10 '12 at 13:04

score 0 · Answer 3 · edited May 10 '12 at 11:03

0

var colorNamesList = dt.Rows
  .Cast<DataRow>()
  .Select(dr => dr["ColorName"].ToString())
  .ToArray();

var colorNames = String.Join("\n", colorNames);

edited May 10 '12 at 11:03

Nikhil Agrawal

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answered May 10 '12 at 11:02

Geert Baeyaert

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1
4

score 0 · Answer 4 · answered May 10 '12 at 11:10

0

int count = 0;
foreach (DataRow dr in dt.Rows)
{
    count++;
    ColorNames +=dr["ColorName"].ToString();
    if (count < dt.Rows.Count)
        ColorNames += "\n";
}

answered May 10 '12 at 11:10

Darshana

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Exclude last element in a loop

4 Answers4