将DataTable转换为CSV流 [英] Convert DataTable to CSV stream

问题描述

目前有一个DataTable，但希望通过WebHandler将其流式传输给用户。 FileHelpers 具有 CommonEngine.DataTableToCsv（dt，file.csv）。但是它将其保存到文件。如何将它保存到流？我知道如何做，当我知道高级中的列或他们不改变，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.

如果我知道刚刚创建的类的列：

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，我不知道列之前，我不能创建类。

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篇文章：

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 ? "\n" : ",");
        }

        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 ? "\n" : ",");
            }
        }

        return result.ToString();
    }
}

并测试：

  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());
  }

编辑：重新提出您的意见：

Re your comments:

这取决于你想要的csv格式，但一般如果文本包含特殊字符，你想把它括在双引号，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，如果是，则用双引号将文本括起来。至于.NET 2.0的东西，只需在你的类中创建一个帮助方法，或删除方法声明中的这个词，并像这样调用：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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