Develop Reference

Transfer text file items with degree symbol to datagridview

I am trying to input items in datagridview using text file.
I have below code to transfer the values of a csv file to my datagridview.
private void TransfertoDataGridView()
{
try
{
string SelectedReport = ReportsFilename;
System.IO.StreamReader file = new System.IO.StreamReader(SelectedReport);
string[] columnnames = file.ReadLine().Split(',');
DataTable dt = new DataTable();
foreach (string c in columnnames)
{
dt.Columns.Add(c);
}
dataGridView1.DataSource = null;
string newline;
while ((newline = file.ReadLine()) != null)
{
if (newline != "")
{
DataRow dr = dt.NewRow();
string[] values = newline.Split(',');
for (int i = 0; i < values.Length; i++)
{
try
{
dr[i] = values[i];
}
catch { }
}
dt.Rows.Add(dr);
}
}
file.Close();
dataGridView1.DataSource = dt;
this.dataGridView1.Columns[0].Visible = false;
}
catch
{
dataGridView1.DataSource = null;
}
}
Below is how my csv file looks like,
Column D has items with degree symbol.
And when I run the code, it transfers all the cell values but replaces the degree symbol with question mark "?".
I need expert help on how I can input the degree symbol to the datagridview.
Thank you very much in advanced for the help.

You can use something like this:
string str = "this is my string with a � sign like this.";
str = str.Replace('�', '°');
As a result:
this is my string with a ° sign like this.
If String like � then it will replace a ° sign.
Any symbol I guess you can do it with a replace function.

Method to return file rather than writing to file

I have the following method to create csv files - it creates a file in a specified directory.
How do I amend this method to return the created file rather than writing to disk?
public void CreateCSV(DataTable dt,string aTitle)
{
string filePath = String.Concat(#"P:\folderX\",aTitle,#"-",this.guid,#".csv");
string delimiter = ",";
//size of the datatable
int NumRows = dt.Rows.Count;
int NumCols = dt.Columns.Count;
StringBuilder sb = new StringBuilder();
List<string> CsvRow = new List<string>();
//try to deal with the headers first
foreach(DataColumn c in dt.Columns)
{
CsvRow.Add(c.ColumnName.ToString());
}
sb.AppendLine(string.Join(delimiter,CsvRow));
//now add the bulk of the data
foreach(DataRow r in dt.Rows)
{
CsvRow.Clear();
//go through each column adding to a list of strings
foreach(DataColumn c in dt.Columns)
{
CsvRow.Add(r[c.ColumnName].ToString());
}
sb.AppendLine(string.Join(delimiter,CsvRow));
}
File.WriteAllText(filePath,sb.ToString());
}

How can I turn a DataTable to a CSV?

Could somebody please tell me why the following code is not working. The data is saved into the csv file, however the data is not separated. It all exists within the first cell of each row.
StringBuilder sb = new StringBuilder();
foreach (DataColumn col in dt.Columns)
{
sb.Append(col.ColumnName + ',');
}
sb.Remove(sb.Length - 1, 1);
sb.Append(Environment.NewLine);
foreach (DataRow row in dt.Rows)
{
for (int i = 0; i < dt.Columns.Count; i++)
{
sb.Append(row[i].ToString() + ",");
}
sb.Append(Environment.NewLine);
}
File.WriteAllText("test.csv", sb.ToString());
Thanks.

The following shorter version opens fine in Excel, maybe your issue was the trailing comma
.net = 3.5
StringBuilder sb = new StringBuilder();
string[] columnNames = dt.Columns.Cast<DataColumn>().
Select(column => column.ColumnName).
ToArray();
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in dt.Rows)
{
string[] fields = row.ItemArray.Select(field => field.ToString()).
ToArray();
sb.AppendLine(string.Join(",", fields));
}
File.WriteAllText("test.csv", sb.ToString());
.net >= 4.0
And as Tim pointed out, if you are on .net>=4, you can make it even shorter:
StringBuilder sb = new StringBuilder();
IEnumerable<string> columnNames = dt.Columns.Cast<DataColumn>().
Select(column => column.ColumnName);
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in dt.Rows)
{
IEnumerable<string> fields = row.ItemArray.Select(field => field.ToString());
sb.AppendLine(string.Join(",", fields));
}
File.WriteAllText("test.csv", sb.ToString());
As suggested by Christian, if you want to handle special characters escaping in fields, replace the loop block by:
foreach (DataRow row in dt.Rows)
{
IEnumerable<string> fields = row.ItemArray.Select(field =>
string.Concat("\"", field.ToString().Replace("\"", "\"\""), "\""));
sb.AppendLine(string.Join(",", fields));
}
And last suggestion, you could write the csv content line by line instead of as a whole document, to avoid having a big document in memory.

I wrapped this up into an extension class, which allows you to call:
myDataTable.WriteToCsvFile("C:\\MyDataTable.csv");
on any DataTable.
public static class DataTableExtensions
{
public static void WriteToCsvFile(this DataTable dataTable, string filePath)
{
StringBuilder fileContent = new StringBuilder();
foreach (var col in dataTable.Columns)
{
fileContent.Append(col.ToString() + ",");
}
fileContent.Replace(",", System.Environment.NewLine, fileContent.Length - 1, 1);
foreach (DataRow dr in dataTable.Rows)
{
foreach (var column in dr.ItemArray)
{
fileContent.Append("\"" + column.ToString() + "\",");
}
fileContent.Replace(",", System.Environment.NewLine, fileContent.Length - 1, 1);
}
System.IO.File.WriteAllText(filePath, fileContent.ToString());
}
}

A new extension function based on Paul Grimshaw's answer. I cleaned it up and added the ability to handle unexpected data. (Empty Data, Embedded Quotes, and comma's in the headings...)
It also returns a string which is more flexible. It returns Null if the table object does not contain any structure.
public static string ToCsv(this DataTable dataTable) {
StringBuilder sbData = new StringBuilder();
// Only return Null if there is no structure.
if (dataTable.Columns.Count == 0)
return null;
foreach (var col in dataTable.Columns) {
if (col == null)
sbData.Append(",");
else
sbData.Append("\"" + col.ToString().Replace("\"", "\"\"") + "\",");
}
sbData.Replace(",", System.Environment.NewLine, sbData.Length - 1, 1);
foreach (DataRow dr in dataTable.Rows) {
foreach (var column in dr.ItemArray) {
if (column == null)
sbData.Append(",");
else
sbData.Append("\"" + column.ToString().Replace("\"", "\"\"") + "\",");
}
sbData.Replace(",", System.Environment.NewLine, sbData.Length - 1, 1);
}
return sbData.ToString();
}
You call it as follows:
var csvData = dataTableOject.ToCsv();

If your calling code is referencing the System.Windows.Forms assembly, you may consider a radically different approach.
My strategy is to use the functions already provided by the framework to accomplish this in very few lines of code and without having to loop through columns and rows. What the code below does is programmatically create a DataGridView on the fly and set the DataGridView.DataSource to the DataTable. Next, I programmatically select all the cells (including the header) in the DataGridView and call DataGridView.GetClipboardContent(), placing the results into the Windows Clipboard. Then, I 'paste' the contents of the clipboard into a call to File.WriteAllText(), making sure to specify the formatting of the 'paste' as TextDataFormat.CommaSeparatedValue.
Here is the code:
public static void DataTableToCSV(DataTable Table, string Filename)
{
using(DataGridView dataGrid = new DataGridView())
{
// Save the current state of the clipboard so we can restore it after we are done
IDataObject objectSave = Clipboard.GetDataObject();
// Set the DataSource
dataGrid.DataSource = Table;
// Choose whether to write header. Use EnableWithoutHeaderText instead to omit header.
dataGrid.ClipboardCopyMode = DataGridViewClipboardCopyMode.EnableAlwaysIncludeHeaderText;
// Select all the cells
dataGrid.SelectAll();
// Copy (set clipboard)
Clipboard.SetDataObject(dataGrid.GetClipboardContent());
// Paste (get the clipboard and serialize it to a file)
File.WriteAllText(Filename,Clipboard.GetText(TextDataFormat.CommaSeparatedValue));
// Restore the current state of the clipboard so the effect is seamless
if(objectSave != null) // If we try to set the Clipboard to an object that is null, it will throw...
{
Clipboard.SetDataObject(objectSave);
}
}
}
Notice I also make sure to preserve the contents of the clipboard before I begin, and restore it once I'm done, so the user does not get a bunch of unexpected garbage next time the user tries to paste. The main caveats to this approach is 1) Your class has to reference System.Windows.Forms, which may not be the case in a data abstraction layer, 2) Your assembly will have to be targeted for .NET 4.5 framework, as DataGridView does not exist in 4.0, and 3) The method will fail if the clipboard is being used by another process.
Anyways, this approach may not be right for your situation, but it is interesting none the less, and can be another tool in your toolbox.

I did this recently but included double quotes around my values.
For example, change these two lines:
sb.Append("\"" + col.ColumnName + "\",");
...
sb.Append("\"" + row[i].ToString() + "\",");

Try changing sb.Append(Environment.NewLine); to sb.AppendLine();.
StringBuilder sb = new StringBuilder();
foreach (DataColumn col in dt.Columns)
{
sb.Append(col.ColumnName + ',');
}
sb.Remove(sb.Length - 1, 1);
sb.AppendLine();
foreach (DataRow row in dt.Rows)
{
for (int i = 0; i < dt.Columns.Count; i++)
{
sb.Append(row[i].ToString() + ",");
}
sb.AppendLine();
}
File.WriteAllText("test.csv", sb.ToString());

4 lines of code:
public static string ToCSV(DataTable tbl)
{
StringBuilder strb = new StringBuilder();
//column headers
strb.AppendLine(string.Join(",", tbl.Columns.Cast<DataColumn>()
.Select(s => "\"" + s.ColumnName + "\"")));
//rows
tbl.AsEnumerable().Select(s => strb.AppendLine(
string.Join(",", s.ItemArray.Select(
i => "\"" + i.ToString() + "\"")))).ToList();
return strb.ToString();
}
Note that the ToList() at the end is important; I need something to force an expression evaluation. If I was code golfing, I could use Min() instead.
Also note that the result will have a newline at the end because of the last call to AppendLine(). You may not want this. You can simply call TrimEnd() to remove it.

Try to put ; instead of ,
Hope it helps

The error is the list separator.
Instead of writing sb.Append(something... + ',') you should put something like sb.Append(something... + System.Globalization.CultureInfo.CurrentCulture.TextInfo.ListSeparator);
You must put the list separator character configured in your operating system (like in the example above), or the list separator in the client machine where the file is going to be watched. Another option would be to configure it in the app.config or web.config as a parammeter of your application.

To write to a file, I think the following method is the most efficient and straightforward: (You can add quotes if you want)
public static void WriteCsv(DataTable dt, string path)
{
using (var writer = new StreamWriter(path)) {
writer.WriteLine(string.Join(",", dt.Columns.Cast<DataColumn>().Select(dc => dc.ColumnName)));
foreach (DataRow row in dt.Rows) {
writer.WriteLine(string.Join(",", row.ItemArray));
}
}
}

Read this and this?
A better implementation would be
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" : ",");
}
}
File.WriteAllText("test.csv", result.ToString());

To mimic Excel CSV:
public static string Convert(DataTable dt)
{
StringBuilder sb = new StringBuilder();
IEnumerable<string> columnNames = dt.Columns.Cast<DataColumn>().
Select(column => column.ColumnName);
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in dt.Rows)
{
IEnumerable<string> fields = row.ItemArray.Select(field =>
{
string s = field.ToString().Replace("\"", "\"\"");
if(s.Contains(','))
s = string.Concat("\"", s, "\"");
return s;
});
sb.AppendLine(string.Join(",", fields));
}
return sb.ToString().Trim();
}

Here is an enhancement to vc-74's post that handles commas the same way Excel does. Excel puts quotes around data if the data has a comma but doesn't quote if the data doesn't have a comma.
public static string ToCsv(this DataTable inDataTable, bool inIncludeHeaders = true)
{
var builder = new StringBuilder();
var columnNames = inDataTable.Columns.Cast<DataColumn>().Select(column => column.ColumnName);
if (inIncludeHeaders)
builder.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in inDataTable.Rows)
{
var fields = row.ItemArray.Select(field => field.ToString().WrapInQuotesIfContains(","));
builder.AppendLine(string.Join(",", fields));
}
return builder.ToString();
}
public static string WrapInQuotesIfContains(this string inString, string inSearchString)
{
if (inString.Contains(inSearchString))
return "\"" + inString+ "\"";
return inString;
}

Here is my solution, based on previous answers by Paul Grimshaw and Anthony VO.
I've submitted the code in a C# project on Github.
My main contribution is to eliminate explicitly creating and manipulating a StringBuilder and instead working only with IEnumerable. This avoids the allocation of a big buffer in memory.
public static class Util
{
public static string EscapeQuotes(this string self) {
return self?.Replace("\"", "\"\"") ?? "";
}
public static string Surround(this string self, string before, string after) {
return $"{before}{self}{after}";
}
public static string Quoted(this string self, string quotes = "\"") {
return self.Surround(quotes, quotes);
}
public static string QuotedCSVFieldIfNecessary(this string self)
{
return (self == null) ? "" : (self.Contains('"') || self.Contains('\r') || self.Contains('\n') || self.Contains(',')) ? self.Quoted() : self;
}
public static string ToCsvField(this string self) {
return self.EscapeQuotes().QuotedCSVFieldIfNecessary();
}
public static string ToCsvRow(this IEnumerable<string> self){
return string.Join(",", self.Select(ToCsvField));
}
public static IEnumerable<string> ToCsvRows(this DataTable self) {
yield return self.Columns.OfType<object>().Select(c => c.ToString()).ToCsvRow();
foreach (var dr in self.Rows.OfType<DataRow>())
yield return dr.ItemArray.Select(item => item.ToString()).ToCsvRow();
}
public static void ToCsvFile(this DataTable self, string path) {
File.WriteAllLines(path, self.ToCsvRows());
}
}
This approach combines nicely with converting IEnumerable to DataTable as asked here.

StringBuilder sb = new StringBuilder();
SaveFileDialog fileSave = new SaveFileDialog();
IEnumerable<string> columnNames = tbCifSil.Columns.Cast<DataColumn>().
Select(column => column.ColumnName);
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in tbCifSil.Rows)
{
IEnumerable<string> fields = row.ItemArray.Select(field =>string.Concat("\"", field.ToString().Replace("\"", "\"\""), "\""));
sb.AppendLine(string.Join(",", fields));
}
fileSave.ShowDialog();
File.WriteAllText(fileSave.FileName, sb.ToString());

public void ExpoetToCSV(DataTable dtDataTable, string strFilePath)
{
StreamWriter sw = new StreamWriter(strFilePath, false);
//headers
for (int i = 0; i < dtDataTable.Columns.Count; i++)
{
sw.Write(dtDataTable.Columns[i].ToString().Trim());
if (i < dtDataTable.Columns.Count - 1)
{
sw.Write(",");
}
}
sw.Write(sw.NewLine);
foreach (DataRow dr in dtDataTable.Rows)
{
for (int i = 0; i < dtDataTable.Columns.Count; i++)
{
if (!Convert.IsDBNull(dr[i]))
{
string value = dr[i].ToString().Trim();
if (value.Contains(','))
{
value = String.Format("\"{0}\"", value);
sw.Write(value);
}
else
{
sw.Write(dr[i].ToString().Trim());
}
}
if (i < dtDataTable.Columns.Count - 1)
{
sw.Write(",");
}
}
sw.Write(sw.NewLine);
}
sw.Close();
}

Possibly, most easy way will be to use:
https://github.com/ukushu/DataExporter
especially in case of your data of datatable containing /r/n characters or separator symbol inside of your dataTable cells. Almost all of other answers will not work with such cells.
only you need is to write the following code:
Csv csv = new Csv("\t");//Needed delimiter
var columnNames = dt.Columns.Cast<DataColumn>().
Select(column => column.ColumnName).ToArray();
csv.AddRow(columnNames);
foreach (DataRow row in dt.Rows)
{
var fields = row.ItemArray.Select(field => field.ToString()).ToArray;
csv.AddRow(fields);
}
csv.Save();

Most existing answers can easily cause OutOfMemoryException, so I decided to write my own answer.
DON' T DO THIS:
using a DataSet + StringBuilder causes the data to occupy the memory 3x at once:
Load All Data into DataSet
Copy all data into StringBuilder
Copy the data to string using StringBuilder.ToString();
Instead you should write each row to a FileStream separately. There is no need to create the whole CSV in memory.
Even better, use a DataReader instead DataSet. That way you can read from database billions of records one by one a write the to a file one by one.
If you don't mind using an external library for CSV, I can recommend the most popular CsvHelper, which has no dependencies.
using (var writer = new FileWriter("test.csv"))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
foreach (DataColumn dc in dt.Columns)
{
csv.WriteField(dc.ColumnName);
}
csv.NextRecord();
foreach (DataRow dr in dt.Rows)
{
foreach (DataColumn dc in dt.Columns)
{
csv.WriteField(dr[dc]);
}
csv.NextRecord();
}
writer.ToString().Dump();
}

In case anyone else stumbles on this, I was using File.ReadAllText to get CSV data and then I modified it and wrote it back with File.WriteAllText. The \r\n CRLFs were fine but the \t tabs were ignored when Excel opened it. (All solutions in this thread so far use a comma delimiter but that doesn't matter.) Notepad showed the same format in the resulting file as in the source. A Diff even showed the files as identical. But I got a clue when I opened the file in Visual Studio with a binary editor. The source file was Unicode but the target was ASCII. To fix, I modified both ReadAllText and WriteAllText with third argument set as System.Text.Encoding.Unicode, and from there Excel was able to open the updated file.

Converting DataSet/DataTable to CSV

Please let me know, if there any way to generate CSV files from a DataTable or DataSet? To be specific, without manually iterating through rows of DataTable and concatenating.
Please help

There are several ways to do that.
One of the simplest (IMO) is using FileHelpers Library
FileHelpers.CsvEngine.DataTableToCsv(dataTable, filename);

A relative simple, compact and quite flexible solution could be the following extension method:
public static string ToCsv(this DataTable table, string colSep = "", string rowSep = "\r\n")
{
var format = string.Join(colSep, Enumerable.Range(0, table.Columns.Count)
.Select(i => string.Format("{{{0}}}", i)));
return string.Join(rowSep, table.Rows.OfType<DataRow>()
.Select(i => string.Format(format, i.ItemArray)));
}
Please note that this solution could cause problems with huge amounts of data, in which case you should stream the output. Quoting and formatting would of course make the code more complex.

There is, I hope, also a possible way for doing that:
static void Main(string[] args)
{
DataTable dt = new DataTable("MyTable");
dt.Columns.Add("Id", typeof(int));
dt.Columns.Add("Name", typeof(string));
DataRow dr1 = dt.NewRow();
dr1["Id"] = 1;
dr1["Name"] = "John Smith";
dt.Rows.Add(dr1);
DataRow dr2 = dt.NewRow();
dr2["Id"] = 2;
dr2["Name"] = "John West";
dt.Rows.Add(dr2);
List<DataRow> list = dt.AsEnumerable().ToList();
var strlist = from dr in list
select dr[0] + ", " + dr[1];
var csv = string.Join(Environment.NewLine,strlist);
Console.WriteLine(csv);
}

//Dataset To Xls
ExportDataSetToCsvFile(DS,#"C:\\");
internal static void ExportDataSetToCsvFile(DataSet _DataSet, string DestinationCsvDirectory)
{
try
{
foreach (DataTable DDT in _DataSet.Tables)
{
String MyFile = #DestinationCsvDirectory + "\\_" + DDT.TableName.ToString() + DateTime.Now.ToString("yyyyMMddhhMMssffff") + ".csv";//+ DateTime.Now.ToString("ddMMyyyyhhMMssffff")
using (var outputFile = File.CreateText(MyFile))
{
String CsvText = string.Empty;
foreach (DataColumn DC in DDT.Columns)
{
if (CsvText != "")
CsvText = CsvText + "," + DC.ColumnName.ToString();
else
CsvText = DC.ColumnName.ToString();
}
outputFile.WriteLine(CsvText.ToString().TrimEnd(','));
CsvText = string.Empty;
foreach (DataRow DDR in DDT.Rows)
{
foreach (DataColumn DCC in DDT.Columns)
{
if (CsvText != "")
CsvText = CsvText + "," + DDR[DCC.ColumnName.ToString()].ToString();
else
CsvText = DDR[DCC.ColumnName.ToString()].ToString();
}
outputFile.WriteLine(CsvText.ToString().TrimEnd(','));
CsvText = string.Empty;
}
System.Threading.Thread.Sleep(1000);
}
}
}
catch (Exception Ex)
{
throw Ex;
}
}

So this is a fairly bizarre solution, but it works faster than most as it makes use of the JSON.net library's serialization. This speeds the solution up significantly.
Steps:
Create array of every column name in the data table, should be
simple
Use JSON.net to convert datatable to a json string
string json = JsonConvert.SerializeObject(dt, Formatting.None);
Begin making use of the Replace function on c# strings and strip the
json string of all json formatting.
json = json.Replace("\"", "").Replace("},{", "\n").Replace(":", "").Replace("[{", "").Replace("}]", "");
Then use the array from step 1 to remove all column names from the
json string. You are left with a csv formatted string.
Consider using the array created in step 1 to add the column names
back in as the first row in csv format.

Convert DataTable to CSV stream

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.
If I know the columns I just create the class:
[DelimitedRecord(",")]
public class MailMergeFields
{
[FieldQuoted()]
public string FirstName;
[FieldQuoted()]
public string LastName;
}
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++;
}
Finally write to a stream:
TextWriter writer = new StringWriter();
engine.WriteStream(writer, merge);
context.Response.Write(writer.ToString());
Unfortunately as I don't know the columns before hand, I can't create the class before hand.

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();
}
}
And to test:
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());
}
EDIT: Re your comments:
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);

Update 1
I have modified it to use StreamWriter instead, add an option to check if you need column headers in your output.
public static bool DataTableToCSV(DataTable dtSource, StreamWriter writer, bool includeHeader)
{
if (dtSource == null || writer == null) return false;
if (includeHeader)
{
string[] columnNames = dtSource.Columns.Cast<DataColumn>().Select(column => "\"" + column.ColumnName.Replace("\"", "\"\"") + "\"").ToArray<string>();
writer.WriteLine(String.Join(",", columnNames));
writer.Flush();
}
foreach (DataRow row in dtSource.Rows)
{
string[] fields = row.ItemArray.Select(field => "\"" + field.ToString().Replace("\"", "\"\"") + "\"").ToArray<string>();
writer.WriteLine(String.Join(",", fields));
writer.Flush();
}
return true;
}
As you can see, you can choose the output by initial StreamWriter, if you use
StreamWriter(Stream BaseStream), you can write csv into MemeryStream, FileStream, etc.
Origin
I have an easy datatable to csv function, it serves me well:
public static void DataTableToCsv(DataTable dt, string csvFile)
{
StringBuilder sb = new StringBuilder();
var columnNames = dt.Columns.Cast<DataColumn>().Select(column => "\"" + column.ColumnName.Replace("\"", "\"\"") + "\"").ToArray();
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in dt.Rows)
{
var fields = row.ItemArray.Select(field => "\"" + field.ToString().Replace("\"", "\"\"") + "\"").ToArray();
sb.AppendLine(string.Join(",", fields));
}
File.WriteAllText(csvFile, sb.ToString(), Encoding.Default);
}

If you can turn your datatable into an IEnumerable this should work for you...
Response.Clear();
Response.Buffer = true;
Response.AddHeader("content-disposition", "attachment;filename=FileName.csv");
Response.Charset = "";
Response.ContentType = "application/text";
Response.Output.Write(ExampleClass.ConvertToCSV(GetListOfObject(), typeof(object)));
Response.Flush();
Response.End();
public static string ConvertToCSV(IEnumerable col, Type type)
{
StringBuilder sb = new StringBuilder();
StringBuilder header = new StringBuilder();
// Gets all properies of the class
PropertyInfo[] pi = type.GetProperties();
// Create CSV header using the classes properties
foreach (PropertyInfo p in pi)
{
header.Append(p.Name + ",");
}
sb.AppendLine(header.ToString().Remove(header.Length));
foreach (object t in col)
{
StringBuilder body = new StringBuilder();
// Create new item
foreach (PropertyInfo p in pi)
{
object o = p.GetValue(t, null);
body.Append(o.ToString() + ",");
}
sb.AppendLine(body.ToString().Remove(body.Length));
}
return sb.ToString();
}

I don't know if this converted from VB to C# ok but if you don't want quotes around your numbers, you might compare the data type as follows..
public string DataTableToCSV(DataTable dt)
{
StringBuilder sb = new StringBuilder();
if (dt == null)
return "";
try {
// Create the header row
for (int i = 0; i <= dt.Columns.Count - 1; i++) {
// Append column name in quotes
sb.Append("\"" + dt.Columns[i].ColumnName + "\"");
// Add carriage return and linefeed if last column, else add comma
sb.Append(i == dt.Columns.Count - 1 ? "\n" : ",");
}
foreach (DataRow row in dt.Rows) {
for (int i = 0; i <= dt.Columns.Count - 1; i++) {
// Append value in quotes
//sb.Append("""" & row.Item(i) & """")
// OR only quote items that that are equivilant to strings
sb.Append(object.ReferenceEquals(dt.Columns[i].DataType, typeof(string)) || object.ReferenceEquals(dt.Columns[i].DataType, typeof(char)) ? "\"" + row[i] + "\"" : row[i]);
// Append CR+LF if last field, else add Comma
sb.Append(i == dt.Columns.Count - 1 ? "\n" : ",");
}
}
return sb.ToString;
} catch (Exception ex) {
// Handle the exception however you want
return "";
}
}

If you wish to stream the CSV out to the user without creating a file then I found the following to be the simplest method. You can use any extension/method to create the ToCsv() function (which returns a string based on the given DataTable).
var report = myDataTable.ToCsv();
var bytes = Encoding.GetEncoding("iso-8859-1").GetBytes(report);
Response.Buffer = true;
Response.Clear();
Response.AddHeader("content-disposition", "attachment; filename=report.csv");
Response.ContentType = "text/csv";
Response.BinaryWrite(bytes);
Response.End();

I've used the following code, pillaged from someone's blog (pls forgive lack of citation). It takes care of quotations, newline and comma in a reasonably elegant way by quoting out each field value.
/// <summary>
/// Converts the passed in data table to a CSV-style string.
/// </summary>
/// <param name="table">Table to convert</param>
/// <returns>Resulting CSV-style string</returns>
public static string ToCSV(this DataTable table)
{
return ToCSV(table, ",", true);
}
/// <summary>
/// Converts the passed in data table to a CSV-style string.
/// </summary>
/// <param name="table">Table to convert</param>
/// <param name="includeHeader">true - include headers<br/>
/// false - do not include header column</param>
/// <returns>Resulting CSV-style string</returns>
public static string ToCSV(this DataTable table, bool includeHeader)
{
return ToCSV(table, ",", includeHeader);
}
/// <summary>
/// Converts the passed in data table to a CSV-style string.
/// </summary>
/// <param name="table">Table to convert</param>
/// <param name="includeHeader">true - include headers<br/>
/// false - do not include header column</param>
/// <returns>Resulting CSV-style string</returns>
public static string ToCSV(this DataTable table, string delimiter, bool includeHeader)
{
var result = new StringBuilder();
if (includeHeader)
{
foreach (DataColumn column in table.Columns)
{
result.Append(column.ColumnName);
result.Append(delimiter);
}
result.Remove(--result.Length, 0);
result.Append(Environment.NewLine);
}
foreach (DataRow row in table.Rows)
{
foreach (object item in row.ItemArray)
{
if (item is DBNull)
result.Append(delimiter);
else
{
string itemAsString = item.ToString();
// Double up all embedded double quotes
itemAsString = itemAsString.Replace("\"", "\"\"");
// To keep things simple, always delimit with double-quotes
// so we don't have to determine in which cases they're necessary
// and which cases they're not.
itemAsString = "\"" + itemAsString + "\"";
result.Append(itemAsString + delimiter);
}
}
result.Remove(--result.Length, 0);
result.Append(Environment.NewLine);
}
return result.ToString();
}

You can try using something like this.
In this case I used one stored procedure to get more data tables and export all of them
using CSV.
using System;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.IO;
namespace bo
{
class Program
{
static private void CreateCSVFile(DataTable dt, string strFilePath)
{
#region Export Grid to CSV
// Create the CSV file to which grid data will be exported.
StreamWriter sw = new StreamWriter(strFilePath, false);
int iColCount = dt.Columns.Count;
// First we will write the headers.
//DataTable dt = m_dsProducts.Tables[0];
for (int i = 0; i < iColCount; i++)
{
sw.Write(dt.Columns[i]);
if (i < iColCount - 1)
{
sw.Write(";");
}
}
sw.Write(sw.NewLine);
// Now write all the rows.
foreach (DataRow dr in dt.Rows)
{
for (int i = 0; i < iColCount; i++)
{
if (!Convert.IsDBNull(dr[i]))
{
sw.Write(dr[i].ToString());
}
if (i < iColCount -1 )
{
sw.Write(";");
}
}
sw.Write(sw.NewLine);
}
sw.Close();
#endregion
}
static void Main(string[] args)
{
string strConn = "connection string to sql";
string direktorij = #"d:";
SqlConnection conn = new SqlConnection(strConn);
SqlCommand command = new SqlCommand("sp_ado_pos_data", conn);
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add('#skl_id', SqlDbType.Int).Value = 158;
SqlDataAdapter adapter = new SqlDataAdapter(command);
DataSet ds = new DataSet();
adapter.Fill(ds);
for (int i = 0; i < ds.Tables.Count; i++)
{
string datoteka = (string.Format(#"{0}tablea{1}.csv", direktorij, i));
DataTable tabela = ds.Tables[i];
CreateCSVFile(tabela,datoteka );
Console.WriteLine("Generišem tabelu {0}", datoteka);
}
Console.ReadKey();
}
}
}

public void CreateCSVFile(DataTable dt, string strFilePath,string separator)
{
#region Export Grid to CSV
// Create the CSV file to which grid data will be exported.
StreamWriter sw = new StreamWriter(strFilePath, false);
int iColCount = dt.Columns.Count;
for (int i = 0; i < iColCount; i++)
{
sw.Write(dt.Columns[i]);
if (i < iColCount - 1)
{
sw.Write(separator);
}
}
sw.Write(sw.NewLine);
// Now write all the rows.
foreach (DataRow dr in dt.Rows)
{
for (int i = 0; i < iColCount; i++)
{
if (!Convert.IsDBNull(dr[i]))
{
sw.Write(dr[i].ToString());
}
if (i < iColCount - 1)
{
sw.Write(separator);
}
}
sw.Write(sw.NewLine);
}
sw.Close();
#endregion
}

BFree's answer worked for me. I needed to post the stream right to the browser. Which I'd imagine is a common alternative. I added the following to BFree's Main() code to do this:
//StreamReader reader = new StreamReader(stream);
//Console.WriteLine(reader.ReadToEnd());
string fileName = "fileName.csv";
HttpContext.Current.Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
HttpContext.Current.Response.AddHeader("content-disposition", string.Format("attachment;filename={0}", fileName));
stream.Position = 0;
stream.WriteTo(HttpContext.Current.Response.OutputStream);