将数据表转换为 CSV 流 [英] Convert DataTable to CSV stream

问题描述

当前有一个 DataTable，但希望通过 WebHandler 将其流式传输给用户.FileHelpers 有 CommonEngine.DataTableToCsv(dt, "file.csv").但是它会将它保存到一个文件中.如何将其保存到流中?当我知道高级列或它们没有更改时，我知道该怎么做，但我想直接从数据表中生成列标题.

Currently have a DataTable, but wish to stream it to the user via a WebHandler. FileHelpers has CommonEngine.DataTableToCsv(dt, "file.csv"). However it saves it to a file. How can I save it to a stream instead? I know how to do it when I know the columns in advanced or they don't change, but I want to generate the column headings straight from the data table.

如果我知道列，我只需创建类:

If I know the columns I just create the class:

[DelimitedRecord(",")]
public class MailMergeFields
{
    [FieldQuoted()]
    public string FirstName;
    [FieldQuoted()]
    public string LastName;
}

然后使用 FileHelperEngine 并添加记录:

Then use FileHelperEngine and add the records:

FileHelperEngine engine = new FileHelperEngine(typeof(MailMergeFields));

MailMergeFields[] merge = new MailMergeFields[dt.Rows.Count + 1];

// add headers
merge[0] = new MailMergeFields();
merge[0].FirstName = "FirstName";
merge[0].LastName = "LastName";

int i = 1;              
// add records
foreach (DataRow dr in dt.Rows)
{
    merge[i] = new MailMergeFields();
    merge[i].FirstName = dr["Forename"];
    merge[i].LastName = dr["Surname"];
    i++;
}

最后写入流:

TextWriter writer = new StringWriter();
engine.WriteStream(writer, merge);
context.Response.Write(writer.ToString());

不幸的是，由于我事先不知道列，因此我无法事先创建类.

Unfortunately as I don't know the columns before hand, I can't create the class before hand.

推荐答案

你可以自己快速写一些东西:

You can just write something quickly yourself:

public static class Extensions
{
    public static string ToCSV(this DataTable table)
    {
        var result = new StringBuilder();
        for (int i = 0; i < table.Columns.Count; i++)
        {
            result.Append(table.Columns[i].ColumnName);
            result.Append(i == table.Columns.Count - 1 ? "
" : ",");
        }

        foreach (DataRow row in table.Rows)
        {
            for (int i = 0; i < table.Columns.Count; i++)
            {
                result.Append(row[i].ToString());
                result.Append(i == table.Columns.Count - 1 ? "
" : ",");
            }
        }

        return result.ToString();
    }
}

并进行测试:

  public static void Main()
  {
        DataTable table = new DataTable();
        table.Columns.Add("Name");
        table.Columns.Add("Age");
        table.Rows.Add("John Doe", "45");
        table.Rows.Add("Jane Doe", "35");
        table.Rows.Add("Jack Doe", "27");
        var bytes = Encoding.GetEncoding("iso-8859-1").GetBytes(table.ToCSV());
        MemoryStream stream = new MemoryStream(bytes);

        StreamReader reader = new StreamReader(stream);
        Console.WriteLine(reader.ReadToEnd());
  }

重新评论:

这取决于您希望如何格式化 csv，但通常如果文本包含特殊字符，您希望将其括在双引号中，即:my,text".您可以在创建 csv 的代码中添加检查以检查特殊字符并将文本括在双引号中(如果有).至于 .NET 2.0 的东西，只需在您的类中将其创建为辅助方法或删除方法声明中的 this 并像这样调用它:Extensions.ToCsv(table);

It depends on how you want your csv formatted but generally if the text contains special characters, you want to enclose it in double quotes ie: "my,text". You can add checking in the code that creates the csv to check for special characters and encloses the text in double quotes if it is. As for the .NET 2.0 thing, just create it as a helper method in your class or remove the word this in the method declaration and call it like so : Extensions.ToCsv(table);

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