数据表到CSV [英] DataTable To CSV

问题描述

此问题与解析CSV无关.

This question is NOT about parsing a CSV.

使用以下代码从DataTable创建CSV
但这很慢
100行乘14列是4秒
有没有更快的方法?

Using the following code to create a CSV from a DataTable
But it is slow
100 rows by 14 columns is 4 seconds
Is there a faster way?

StringBuilder sb = new StringBuilder();
bool first = true;
int colCount = 0;
foreach (DataColumn dc in DT.Columns)
{
    if (first) first = false; else sb.Append(",");
    sb.Append("\"" + dc.ColumnName +  "\"");
    colCount++;
}
sb.AppendLine();
foreach (DataRow dr in DT.Rows)
{  
    first = true;
    for (int i = 0; i < colCount; i++)
    {
        if (first) first = false; else sb.Append(",");
        sb.Append("\"" + dr[i].ToString().Trim() + "\"");
    }
    sb.AppendLine();
}
return sb.ToString();

StringBuilder在这里不是问题.
从0到100万的负载i在300毫秒内运行

StringBuilder is not the problem here.
Load i from 0 to 1 million runs in 300 milliseconds

StringBuilder sb = new StringBuilder();
Stopwatch sw = new Stopwatch();
sw.Start();
for (int i = 0; i < 1000000; i++)
{
    sb.Append(i.ToString());
}
sw.Stop();
Debug.Write(sw.ElapsedMilliseconds.ToString());

推荐答案

有更快的字符串串联方法以及其他一些逻辑.使用字符串生成器构建整个对象也可能是速度下降的一部分.一个图书馆可能已经考虑了其中的一些问题，并且可能会如某些人所建议的那样执行得更快.

There are faster ways of doing string concatenation and some of the other logic. Using the string builder to build up the whole thing may be part of the slowdown too. A library would have some of these things thought out already and would probably perform faster, as some have suggested.

以下是使用 CsvHelper (我写过)的一些代码.

Here is some code using CsvHelper (which I wrote).

using( var dt = new DataTable() )
{
    dt.Load( dataReader );
    foreach( DataColumn column in dt.Columns )
    {
        csv.WriteField( column.ColumnName );
    }
    csv.NextRecord();

    foreach( DataRow row in dt.Rows )
    {
        for( var i = 0; i < dt.Columns.Count; i++ )
        {
            csv.WriteField( row[i] );
        }
        csv.NextRecord();
    }
}

如果您拥有DataReader，那么您甚至不必使用DataTable，这也可以加快速度.

If you have the DataReader you don't even have to use the DataTable then, which should speed it up some too.

var hasHeaderBeenWritten = false;
while( dataReader.Read() )
{
    if( !hasHeaderBeenWritten )
    {
        for( var i = 0; i < dataReader.FieldCount; i++ )
        {
            csv.WriteField( dataReader.GetName( i ) );
        }
        csv.NextRecord();
        hasHeaderBeenWritten = true;
    }

    for( var i = 0; i < dataReader.FieldCount; i++ )
    {
        csv.WriteField( dataReader[i] );
    }
    csv.NextRecord();
}

这篇关于数据表到CSV的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！