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
– eouw0o83hf, Commented Feb 1, 2012 at 6:20
It also make it synchronous, so you shouldn't use that for large files. — cwharris
– cwharris, Commented Feb 1, 2012 at 6:22

Kyle Trauberman · Accepted Answer · 2012-02-01 06:33:06Z

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 1, 2012 at 6:33

answered Feb 1, 2012 at 6:19

Kyle Trauberman

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6 Comments

Ye Myat Aung Over a year ago

Will it affect the performance if the input data is quite large?

Kyle Trauberman Over a year ago

Potentially, I don't have any data on performance myself. You can run your own tests to see.

Ye Myat Aung Over a year ago

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?

Sergey Vyacheslavovich Brunov Over a year ago

string.Join(",", lineValues.Skip(1));

Kyle Trauberman Over a year ago

@Ye Myat Aung lineValues is a List<string>. 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.

|

eouw0o83hf · Accepted Answer · 2012-02-01 06:19:33Z

2

.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.

answered Feb 1, 2012 at 6:19

eouw0o83hf

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Comments

Community · Accepted Answer · 2017-05-23 11:56:39Z

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, 2017 at 11:56

CommunityBot

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answered Feb 1, 2012 at 6:20

cwharris

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