因此，我必須在本作業中使用一個結構體，并且需要對一個名為 Country_databas.csv 的 CSV 文件進行排序。到目前為止，我已經制作了該結構體和一個列表，用于處理 CSV 上一行的每個分割。但是，我正在努力將 CSV 的每個拆分添加到其各自的列表中，以便我可以對它們進行排序。編輯：抱歉，我剛剛意識到我錯過了 CSV 在線的最后一個分割，即第一行的“Kabul”。我的 CSV 的前 4 行：1. Afghanistan,Asia,652230,25500100,20364000000,Kabul2. Albania,Europe,28748,2821977,12044000000,Tirana3. Algeria,Africa,2381741,38700000,207021000000,Algiers4. Andorra,Europe,468,76098,3222000000,Andorra la Vella代碼：namespace CSVFileUtility{ public struct CSVline { public List<string> Country; public List<string> Continent; public List<int> popualtion; public List<int> landmass; public List<long> Bignum; public CSVline(List<string> Country, List<string> Continent, List<int> popualtion, List<int> landmass, List<long> Bignum) { this.Country = Country; this.Continent = Continent; this.popualtion = popualtion; this.landmass = landmass; this.Bignum = Bignum; } } class Program { static void Main(string[] args) { string line; CSVline csv = new CSVline(); using ( StreamReader sr = new StreamReader(@"filepath of csv") ) { try { while ( ( line = sr.ReadLine() ) != null ) { var values = line.Split(','); csv.Country.Add(values[1]); } } catch ( Exception ex ) { Console.WriteLine("The file could not be read {0}", ex); } } } }}這會導致錯誤“無法讀取文件 System.NullReferenceException：對象引用未設置到對象的實例”，該錯誤來自行“csv.Country.Add(values[1]);”
1 回答
慕俠2389804
TA貢獻1719條經驗 獲得超6個贊
您的結構錯誤，您不應在結構中添加列表，結構的每條記錄應僅包含一個國家/地區的條目，然后您可以像這樣創建結構列表：
public struct CSVline
{
public string Country;
public string Continent;
public int popualtion;
public int landmass;
public long Bignum;
public CSVline(string Country, string Continent, int popualtion, int landmass, long Bignum)
{
this.Country = Country;
this.Continent = Continent;
this.popualtion = popualtion;
this.landmass = landmass;
this.Bignum = Bignum;
}
}
那么你可以這樣做：
string line;
var csv = new List<CSVline>();
using (StreamReader sr = new StreamReader(@"filepath of csv"))
{
try
{
while ((line = sr.ReadLine()) != null)
{
var values = line.Split(',');
csv.Add(new CSVline(values[0],values[1],values[2],values[3],values[4]));
}
}
catch (Exception ex)
{
Console.WriteLine("The file could not be read {0}", ex);
}
}
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