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
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);
}
}
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);
}
}
手动编写csv文件可能很困难，因为数据可能包含逗号和换行符。我建议您使用现有的库。
这个问题提到了几个选项。
c#中有CSV读取器/写入器库吗?
处理逗号
对于在使用string.Format(…)时处理值中的逗号，以下方法对我有用:
var newLine = string.Format("\"{0}\",\"{1}\",\"{2}\"",
first,
second,
third
);
csv.AppendLine(newLine);
所以把它和约翰的答案结合起来，看起来是这样的:
//before your loop
var csv = new StringBuilder();
//in your loop
var first = reader[0].ToString();
var second = image.ToString();
//Suggestion made by KyleMit
var newLine = string.Format("\"{0}\",\"{1}\"", first, second);
csv.AppendLine(newLine);
//after your loop
File.WriteAllText(filePath, csv.ToString());
返回CSV文件
如果你只是想返回文件，而不是把它写到一个位置，这是我如何完成它的一个例子:
从存储过程
public FileContentResults DownloadCSV()
{
// I have a stored procedure that queries the information I need
SqlConnection thisConnection = new SqlConnection("Data Source=sv12sql;User ID=UI_Readonly;Password=SuperSecure;Initial Catalog=DB_Name;Integrated Security=false");
SqlCommand queryCommand = new SqlCommand("spc_GetInfoINeed", thisConnection);
queryCommand.CommandType = CommandType.StoredProcedure;
StringBuilder sbRtn = new StringBuilder();
// If you want headers for your file
var header = string.Format("\"{0}\",\"{1}\",\"{2}\"",
"Name",
"Address",
"Phone Number"
);
sbRtn.AppendLine(header);
// Open Database Connection
thisConnection.Open();
using (SqlDataReader rdr = queryCommand.ExecuteReader())
{
while (rdr.Read())
{
// rdr["COLUMN NAME"].ToString();
var queryResults = string.Format("\"{0}\",\"{1}\",\"{2}\"",
rdr["Name"].ToString(),
rdr["Address"}.ToString(),
rdr["Phone Number"].ToString()
);
sbRtn.AppendLine(queryResults);
}
}
thisConnection.Close();
return File(new System.Text.UTF8Encoding().GetBytes(sbRtn.ToString()), "text/csv", "FileName.csv");
}
从列表中
/* To help illustrate */
public static List<Person> list = new List<Person>();
/* To help illustrate */
public class Person
{
public string name;
public string address;
public string phoneNumber;
}
/* The important part */
public FileContentResults DownloadCSV()
{
StringBuilder sbRtn = new StringBuilder();
// If you want headers for your file
var header = string.Format("\"{0}\",\"{1}\",\"{2}\"",
"Name",
"Address",
"Phone Number"
);
sbRtn.AppendLine(header);
foreach (var item in list)
{
var listResults = string.Format("\"{0}\",\"{1}\",\"{2}\"",
item.name,
item.address,
item.phoneNumber
);
sbRtn.AppendLine(listResults);
}
}
return File(new System.Text.UTF8Encoding().GetBytes(sbRtn.ToString()), "text/csv", "FileName.csv");
}
希望这对你们有帮助。
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
