How to concat string to List C#

Question

I was trying to add the strings to the List and export the list as csv file but the result I got is not the way I want. Here is the code -

List<string> values = new List<string>();
using (StreamReader sr = new StreamReader(filePath))
{
    while (sr.Peek() != -1)
    {
        string line = sr.ReadLine();
        List<string> lineValues = line.Split(',').ToList();
        var tempMinInt = 1;
        var tempValue = 1;
        var tempValInt = Convert.ToInt32(lineValues[4]);
        if (tempValInt % 60 != 0)
        {
            tempMinInt = (tempValInt / 60) + 1;
            tempValue = tempMinInt * 30;
        }
        else
        {
            tempMinInt = tempValInt / 60;
            tempValue = tempMinInt * 30;
        }


        values.Add(lineValues + "," + tempValue.ToString());

    }
}

Here is the sample input data:

33083,2011-12-19 05:17:57+06:30,98590149,1876,258
33084,2011-12-19 05:22:28+06:30,98590149,1876,69
33085,2011-12-19 05:23:45+06:30,98590149,1876,151
33086,2011-12-19 05:30:21+06:30,98590149,1876,58
33087,2011-12-19 06:44:19+06:30,949826259,1876,66

And here is the output data:

System.Collections.Generic.List`1[System.String],150
System.Collections.Generic.List`1[System.String],60
System.Collections.Generic.List`1[System.String],90
System.Collections.Generic.List`1[System.String],30
System.Collections.Generic.List`1[System.String],60

Please advice. Thank you.

Also, you should check out File.ReadAllLines in the System.IO namespace. It make importing files line-by-line much easier. — eouw0o83hf, Feb 01 '12 at 06:20
It also make it synchronous, so you shouldn't use that for large files. — cwharris, Feb 01 '12 at 06:22

Kyle Trauberman · Accepted Answer · 2012-02-01T06:33:06.670

5

List<T> does not override ToString, so you'll need to do the leg work here.

You can use string.Join to combine the values of the list into a comma separated string:

string.Join(",", lineValues.ToArray());

Your last line of code posted above will become:

values.Add(string.Join(",", lineValues.ToArray()) + "," + tempValue.ToString());

http://msdn.microsoft.com/en-us/library/57a79xd0.aspx

Alternatively, you can just use line in this code snippet, as lineValues is built from line and you aren't modifying any of the values.

edited Feb 01 '12 at 06:33

answered Feb 01 '12 at 06:19

Kyle Trauberman

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Will it affect the performance if the input data is quite large? – Ye Myat Aung Feb 01 '12 at 06:21
Potentially, I don't have any data on performance myself. You can run your own tests to see. – Kyle Trauberman Feb 01 '12 at 06:23
It works! But could you tell me if there's any difference between lineValues.ToArray() and just lineValues? And also, if I want to skip the first row of the input data, how can I do it? – Ye Myat Aung Feb 01 '12 at 06:39
`string.Join(",", lineValues.Skip(1));` – Sergey Vyacheslavovich Brunov Feb 01 '12 at 06:57
@Ye Myat Aung `lineValues` is a `List`. The `.ToArray` method copies the data to a `string[]` array which the `string.Join` method takes as an argument. Serge is correct. You can use `.Skip(1)` to skip the first row. You'll still need to call `.ToArray` afterwards. – Kyle Trauberman Feb 01 '12 at 07:20
Thank you for the explanation. But I want to skip the first row of te input data at the beginning before I do any calculations (because it contains characters). – Ye Myat Aung Feb 01 '12 at 08:08

score 2 · Answer 2 · answered Feb 01 '12 at 06:19

.NET is trying to turn a List of strings into a string, and it doesn't know how to do this implicitly. I think you should check out string.Join, and use it like:

values.Add(string.Join(",", lineValues) + "," + tempValue.ToString());

This will turn the list of strings into a comma-separated string.

score 0 · Answer 3 · edited May 23 '17 at 11:56

0

What you're looking for is string.Join(",", lineValues)

Try this:

values.Add(string.Join(",", lineValues) + "," + tempValue.ToString());

Also, this won't work if any of those line values contain characters that need to be escaped.

See here for a solution to escaping characters.

edited May 23 '17 at 11:56

Community

1
1

answered Feb 01 '12 at 06:20

cwharris

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How to concat string to List C#

3 Answers3