如何使用CSVHelper在CSV中寫入一個class的列表屬性

Question

目前我有以下 class 結構

class Foo{
    int FooID {get;set;}
    List<Bar> Bars {get;set;};
}

class Bar{
    int BarID {get;set;}    
    string BarProperty1 {get;set;}  
    string BarProperty2 {get;set;}  
    string BarProperty3 {get;set;}
}

現在我想寫一個 CSV 文件，它有一個字段“ID”，它是 Foo 和 Bars ID 的 ID 的混合，rest 應該是 Bar object 的屬性。

這是一些示例對象：

Foo01 ID = 01
List bars = {A, Red, Red, Green; B, Yellow, Red, Red}

Foo02 ID = 02
List bars = {A, Green, Green, Red; B, Red, Purple, Orange; C, White, Black, Red}

現在 CSV 編寫器應該創建一個如下所示的 CSV：

ID;Prop1;Prop2;Prop3
01A;Red;Red;Green
01B;Yellow;Red;Red
02A;Green;Green;Red
02B;Red;Purple;Orange
02C;White;Black;Red

使用 CSVHelper 是否可行，或者我是否需要編寫自己的實現？

Answer 1

不幸的是，您不能直接從單個 object 創建多個 CSV 行。因此您必須展平列表並將它們寫入 CSV 文件。

這是一個工作示例：

public class BarMap : ClassMap<Bar>
{
    public BarMap()
    {
        Map(bar => bar.BarID).Name("Id");
        Map(bar => bar.BarProperty1).Name("Prop1");
        Map(bar => bar.BarProperty2).Name("Prop2");
        Map(bar => bar.BarProperty3).Name("Prop3");
    }
}

string content = null;

using (var memory = new MemoryStream())
using (var writer = new StreamWriter(memory))
using (var csv = new CsvWriter(writer, CultureInfo.GetCultureInfo("en")))
{
    csv.Context.RegisterClassMap<BarMap>();
    // Flatten nested collections into one list
    var bars = foos
        // Would be less typing probably if using AutoMapper to create new instances.
        .SelectMany(foo => foo.Bars.Select(bar => new Bar { BarID = $"{foo.FooID}{bar.BarID}", BarProperty1 = bar.BarProperty1, BarProperty2 = bar.BarProperty2, BarProperty3 = bar.BarProperty3 }));
    csv.WriteRecords(bars);

    writer.Flush();
    memory.Position = 0;

    using (var reader = new StreamReader(memory))
    {
        content = reader.ReadToEnd();
    }
}

Answer 2

您只需要編寫器 object 和嵌套的 for 循環。

public static void Main()
        {
            // set up
            var bars1 = new List<Bar>();
            bars1.Add(new Bar() { BarID = 1, BarProperty1 = "Red", BarProperty2 = "Green", BarProperty3 = "Green" });
            bars1.Add(new Bar() { BarID = 2, BarProperty1 = "White", BarProperty2 = "Green", BarProperty3 = "Black" });
            var bars2 = new List<Bar>();
            bars2.Add(new Bar() { BarID = 1, BarProperty1 = "Pink", BarProperty2 = "Green", BarProperty3 = "Green" });
            bars2.Add(new Bar() {  BarID = 2, BarProperty1 = "White", BarProperty2 = "Green", BarProperty3 = "Black" });
            bars2.Add(new Bar() {  BarID = 2, BarProperty1 = "Cyan", BarProperty2 = "Green", BarProperty3 = "Black" });

            var foo1 = new Foo() { FooID = 1, Bars = bars1 };
            var foo2 = new Foo() { FooID = 2, Bars = bars2 };
            var foos = new List<Foo>() { foo1, foo2 };

            // write CSV
            using (var writer = new StreamWriter("file.csv"))
            using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
            {
                writer.WriteLine("Id,Prop1,Prop2,Prop3");
                foreach (var foo in foos)
                {
                    
                    foreach (var bar in foo.Bars)
                    {
                        writer.Write(foo.FooID);
                        csv.WriteRecord(bar);
                        csv.NextRecord();
                    }
                    
                }
            }
        }

Answer 3

我發現了一種更簡單、更簡單的做事方式：

我基本上創建了一個名為 CSVEntry 的新 Class，它具有所需的屬性，並循環遍歷我的對象以生成所需的條目，然后再使用 CSVHelper 將它們寫入文件。

        foreach (Foo foo in foos)
        {
            foreach (Bar bar in foo.bars)
            {
                CSVEntry CSVEntry = new CSVEntry();
                CSVEntry.id = (foo.id + bar.id);
                CSVEntry.property1 = bar.property1;
                CSVEntry.property2 = bar.property2;
                CSVEntry.property3 = bar.property3;
            
                CSVEntries.Add(CSVEntry);
            }

        }

    public static void writeCSVfile(List<CSVEntry> CSVEntries, String csvPath)
    {

        using (var streamedWriter = new StreamWriter(csvPath))
        {

            using (var csvWriter = new CsvWriter(streamedWriter, System.Globalization.CultureInfo.CurrentUICulture))
            {

                csvWriter.WriteRecords(CSVEntries);

            }

        }

    }