我试图用c#语言一行一行地写入csv文件。这是我的函数

string first = reader[0].ToString();
string second=image.ToString();
string csv = string.Format("{0},{1}\n", first, second);
File.WriteAllText(filePath, csv);

整个函数在循环中运行,每一行都应该写入csv文件。在我的例子中,下一行覆盖了现有的行,最后,我在csv文件中只得到一条记录,这是最后一条记录。如何写入csv文件中的所有行?


当前回答

public static class Extensions
{
    public static void WriteCSVLine(this StreamWriter writer, IEnumerable<string> fields)
    {
        const string q = @"""";
        writer.WriteLine(string.Join(",",
            fields.Select(
                v => (v.Contains(',') || v.Contains('"') || v.Contains('\n') || v.Contains('\r')) ? $"{q}{v.Replace(q, q + q)}{q}" : v
                )));
    }

    public static void WriteCSVLine(this StreamWriter writer, params string[] fields) => WriteCSVLine(writer, (IEnumerable<string>)fields);
}

这将允许您非常简单地编写csv文件。用法:

StreamWriter writer = new ("myfile.csv");
writer.WriteCSVLine("A", "B"); // A,B

其他回答

public static class Extensions
{
    public static void WriteCSVLine(this StreamWriter writer, IEnumerable<string> fields)
    {
        const string q = @"""";
        writer.WriteLine(string.Join(",",
            fields.Select(
                v => (v.Contains(',') || v.Contains('"') || v.Contains('\n') || v.Contains('\r')) ? $"{q}{v.Replace(q, q + q)}{q}" : v
                )));
    }

    public static void WriteCSVLine(this StreamWriter writer, params string[] fields) => WriteCSVLine(writer, (IEnumerable<string>)fields);
}

这将允许您非常简单地编写csv文件。用法:

StreamWriter writer = new ("myfile.csv");
writer.WriteCSVLine("A", "B"); // A,B

你可以使用AppendAllText代替:

File.AppendAllText(filePath, csv);

正如WriteAllText的文档所说:

如果目标文件已经存在,那么它将被覆盖

此外,请注意您当前的代码没有使用适当的新行,例如在记事本中,您将看到它都是一个长行。将代码更改为这样,以获得正确的新行:

string csv = string.Format("{0},{1}{2}", first, image, Environment.NewLine);

消除覆盖问题的一个简单方法是使用File。将行追加到文件的末尾作为

void Main()
{
    using (System.IO.StreamWriter sw = System.IO.File.AppendText("file.txt"))
    {          
        string first = reader[0].ToString();
        string second=image.ToString();
        string csv = string.Format("{0},{1}\n", first, second);
        sw.WriteLine(csv);
    }
} 

我使用双解析解决方案,因为它非常容易维护

// Prepare the values
var allLines = (from trade in proposedTrades
                select new object[] 
                { 
                    trade.TradeType.ToString(), 
                    trade.AccountReference, 
                    trade.SecurityCodeType.ToString(), 
                    trade.SecurityCode, 
                    trade.ClientReference, 
                    trade.TradeCurrency, 
                    trade.AmountDenomination.ToString(), 
                    trade.Amount, 
                    trade.Units, 
                    trade.Percentage, 
                    trade.SettlementCurrency, 
                    trade.FOP, 
                    trade.ClientSettlementAccount, 
                    string.Format("\"{0}\"", trade.Notes),                             
                }).ToList();

// Build the file content
var csv = new StringBuilder();
allLines.ForEach(line => 
{
    csv.AppendLine(string.Join(",", line));            
});

File.WriteAllText(filePath, csv.ToString());

而不是每次调用AppendAllText(),你可以考虑打开文件一次,然后写整个内容一次:

var file = @"C:\myOutput.csv";

using (var stream = File.CreateText(file))
{
    for (int i = 0; i < reader.Count(); i++)
    {
        string first = reader[i].ToString();
        string second = image.ToString();
        string csvRow = string.Format("{0},{1}", first, second);

        stream.WriteLine(csvRow);
    }
}