将 CSV 数据导入 C# 类

Question

I know how to read and display a line of a .csv file. Now I would like to parse that file, store its contents in arrays, and use those arrays as values for some classes I created.

I'd like to learn how though.

Here is an example:

basketball,2011/01/28,Rockets,Blazers,98,99
baseball,2011/08/22,Yankees,Redsox,4,3

As you can see, each field is separated by commas. I've created the Basketball.cs and Baseball classes which is an extension of the Sport.cs class, which has the fields:

private string sport;
private string date;
private string team1;
private string team2;
private string score;

I understand that this is simplistic, and that there's better ways of storing this info, ie creating classes for each team, making the date a DateType datatype, and more of the same but I'd like to know how to input this information into the classes.

I'm assuming this has something to do with getters and setters... I've also read of dictionaries and collections, but I'd like to start simple by storing them all in arrays... (If that makes sense... Feel free to correct me).

Here is what I have so far. All it does is read the csv and parrot out its contents on the Console:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace Assign01
{
    class Program
    {
        static void Main(string[] args)
        {
            string line;
            FileStream aFile = new FileStream("../../sportsResults.csv", FileMode.Open);
            StreamReader sr = new StreamReader(aFile);

            // read data in line by line
            while ((line = sr.ReadLine()) != null)
            {
                Console.WriteLine(line);
                line = sr.ReadLine();
            }
            sr.Close();
        }
    }
}

Help would be much appreciated.

Answer 1

For a resilient, fast, and low effort solution, you can use CsvHelper which handles a lot of code and edge cases and has pretty good documentation

First, install the CsvHelper package on Nuget

a) CSV with Headers

If your csv has headers like this:

sport,date,team 1,team 2,score 1,score 2
basketball,2011/01/28,Rockets,Blazers,98,99
baseball,2011/08/22,Yankees,Redsox,4,3

You can add attributes to your class to map the field names to your class names like this:

public class SportStats
{
    [Name("sport")]
    public string Sport { get; set; }
    [Name("date")]
    public DateTime Date { get; set; }
    [Name("team 1")]
    public string TeamOne { get; set; }
    [Name("team 2")]
    public string TeamTwo { get; set; }
    [Name("score 1")]
    public int ScoreOne { get; set; }
    [Name("score 2")]
    public int ScoreTwo { get; set; }
}

And then invoke like this:

List<SportStats> records;

using (var reader = new StreamReader(@".\stats.csv"))
using (var csv = new CsvReader(reader))
{
    records = csv.GetRecords<SportStats>().ToList();
}

b) CSV without Headers

If your csv doesn't have headers like this:

basketball,2011/01/28,Rockets,Blazers,98,99
baseball,2011/08/22,Yankees,Redsox,4,3

You can add attributes to your class and map to the CSV ordinally by position like this:

public class SportStats
{
    [Index(0)]
    public string Sport { get; set; }
    [Index(1)]
    public DateTime Date { get; set; }
    [Index(2)]
    public string TeamOne { get; set; }
    [Index(3)]
    public string TeamTwo { get; set; }
    [Index(4)]
    public int ScoreOne { get; set; }
    [Index(5)]
    public int ScoreTwo { get; set; }
}

And then invoke like this:

List<SportStats> records;

using (var reader = new StreamReader(@".\stats.csv"))
using (var csv = new CsvReader(reader))
{
    csv.Configuration.HasHeaderRecord = false;
    records = csv.GetRecords<SportStats>().ToList();
}

Further Reading

• Reading CSV file and storing values into an array (295🡅)
• Parsing CSV files in C#, with header (245🡅)
• Import CSV file to strongly typed data structure in .Net (104🡅)
• Reading a CSV file in .NET? (45🡅)
• Is there a “proper” way to read CSV files (17🡅)
• ... many more

Answer 2

Creating array to keep the information is not a very good idea, as you don't know how many lines will be in the input file. What would be the initial size of your Array ?? I would advise you to use for example a Generic List to keep the information (Eg List<>).

You can also add a constructor to your Sport Class that accepts an array (result of the split action as described in above answer.

Additionally you can provide some conversions in the setters

public class Sport
{
    private string sport;
    private DateTime date;
    private string team1;
    private string team2;
    private string score;

    public Sport(string[] csvArray)
    {
        this.sport = csvArray[0];
        this.team1 = csvArray[2];
        this.team2 = csvArray[3];
        this.date = Convert.ToDateTime(csvArray[1]);
        this.score = String.Format("{0}-{1}", csvArray[4], csvArray[5]);
    }

Just for simplicity I wrote the Convert Method, but keep in mind this is also not a very safe way unless you are sure that the DateField always contains valid Dates and Score always contains Numeric Values. You can try other safer methods like tryParse or some Exception Handling.

I all honesty, it must add that the above solution is simple (as requested), on a conceptual level I would advise against it. Putting the mapping logic between attributes and the csv-file in the class will make the sports-class too dependent on the file itself and thus less reusable. Any later changes in the file structure should then be reflected in your class and can often be overlooked. Therefore it would be wiser to put your “mapping & conversion” logic in the main program and keep your class a clean as possible

(Changed your "Score" issue by formatting it as 2 strings combined with a hyphen)

Answer 3

splitting the sting into arrays to get the data can be error prone and slow. Try using an OLE data provider to read the CSV as if it were a table in an SQL database, this way you can use a WHERE clause to filter the results.

App.Config :

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="csv" providerName="System.Data.OleDb" connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source='C:\CsvFolder\';Extended Properties='text;HDR=Yes;FMT=Delimited';" />
  </connectionStrings>
</configuration>

program.cs :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Configuration;
using System.Data;
using System.Data.Common;

namespace CsvImport
{
    class Stat
    {
        public string Sport { get; set; }
        public DateTime Date { get; set; }
        public string TeamOne { get; set; }
        public string TeamTwo { get; set; }
        public int Score { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            ConnectionStringSettings csv = ConfigurationManager.ConnectionStrings["csv"];
            List<Stat> stats = new List<Stat>();

            using (OleDbConnection cn = new OleDbConnection(csv.ConnectionString))
            {
                cn.Open();
                using (OleDbCommand cmd = cn.CreateCommand())
                {
                    cmd.CommandText = "SELECT * FROM [Stats.csv]";
                    cmd.CommandType = CommandType.Text;
                    using (OleDbDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        int fieldSport = reader.GetOrdinal("sport");
                        int fieldDate = reader.GetOrdinal("date");
                        int fieldTeamOne = reader.GetOrdinal("teamone");
                        int fieldTeamTwo = reader.GetOrdinal("teamtwo");
                        int fieldScore = reader.GetOrdinal("score");

                        foreach (DbDataRecord record in reader)
                        {
                            stats.Add(new Stat
                            {
                                Sport = record.GetString(fieldSport),
                                Date = record.GetDateTime(fieldDate),
                                TeamOne = record.GetString(fieldTeamOne),
                                TeamTwo = record.GetString(fieldTeamTwo),
                                Score = record.GetInt32(fieldScore)
                            });
                        }
                    }
                }
            }

            foreach (Stat stat in stats)
            {
                Console.WriteLine("Sport: {0}", stat.Sport);
            }
        }
    }
}

Here's how the csv should look

stats.csv :

sport,date,teamone,teamtwo,score
basketball,28/01/2011,Rockets,Blazers,98
baseball,22/08/2011,Yankees,Redsox,4

Answer 4

While there are a lot of libraries that will make csv reading easy (see: here ), all you need to do right now that you have the line, is to split it.

String[] csvFields = line.Split(",");

Now assign each field to the appropriate member

sport = csvFields[0];
date = csvFields[1];
//and so on

This will however overwrite the values each time you read a new line, so you need to pack the values into a class and save the instances of that class to a list.

Answer 5

Linq also has a solution for this and you can define your output as either a List or an Array. In the example below there is a class that as the definition of the data and data types.

var modelData = File.ReadAllLines(dataFile)
                   .Skip(1)
                   .Select(x => x.Split(','))
                   .Select(dataRow => new TestModel
                   {
                       Column1 = dataRow[0],
                       Column2 = dataRow[1],
                       Column3 = dataRow[2],
                       Column4 = dataRow[3]
                   }).ToList(); // Or you can use .ToArray()

Answer 6

// use "Microsoft.VisualBasic.dll"

using System;
using Microsoft.VisualBasic.FileIO;

class Program {
    static void Main(string[] args){
        using(var csvReader = new TextFieldParser(@"sportsResults.csv")){
            csvReader.SetDelimiters(new string[] {","});
            string [] fields;
            while(!csvReader.EndOfData){
                fields = csvReader.ReadFields();
                Console.WriteLine(String.Join(",",fields));//replace make instance
            }
        }
    }
}

Answer 7

Below is for newbie and eye catching solution that most newbie like to try and error please don;t forget to add System.Core.dll in references Import namespace in your .cs file : using System.Linq;

Perhaps add iterator will be better code

private static IEnumerable<String> GetDataPerLines()
{
    FileStream aFile = new FileStream("sportsResults.csv",FileMode.Open);             
    StreamReader sr = new StreamReader(aFile); 
    while ((line = sr.ReadLine()) != null)             
    { 
        yield return line;
    }             
    sr.Close(); 
}

static void Main(string[] args)
{
    var query = from data in GetDataPerLines()
          let splitChr = data.Split(",".ToCharArray())
                select new Sport
    {
       sport = splitChr[0],
       date = splitChr[1],.. and so on
    }

    foreach (var item in query)
    {
        Console.Writeline(" Sport = {0}, in date when {1}",item.sport,item.date);
    }
}

Maybe like this, the sample above is creating your own iteration using yield (please look at MSDN documentation for that) and create collection based on your string.

Let me know if I write the code wrong since I don;t have Visual studio when I write the answer. For your knowledge, an array one dimension like "Sport[]" will translate into CLR IEnumerable