How can I get CSV file encoding UTF-8 in C#.Net?

SuSanda,
I'm not sure about your current code or your actual text you're trying to save, but this might get you in the right direction.

using(var sw = new StreamWriter("testfile_utf8.csv", false, Encoding.UTF8)) { sw.WriteLine("頼もう"); } 

If you open that file in Excel, it will show the Japanese text as expected.
If you do not include the Encoding.UTF8 parameter, it will display gibberish.

I hope that's what you're looking for.

This code helps to text from a csv file to save it as a encoded csv file. To use it Call as below and save it.

GetCSVFileContent("Your_CSV_FileName")

protected byte[] GetCSVFileContent(string fileName) { StringBuilder sb = new StringBuilder(); using (StreamReader sr = new StreamReader(fileName, Encoding.Default, true)) { String line; // Read and display lines from the file until the end of // the file is reached. while ((line = sr.ReadLine()) != null) { sb.AppendLine(line); } } string allines = sb.ToString(); UTF8Encoding utf8 = new UTF8Encoding(); var preamble = utf8.GetPreamble(); var data = utf8.GetBytes(allines); return data; } 

 StringBuilder sb = new StringBuilder(); var columnNames = dt.Columns.Cast<DataColumn>().Select(column => column.ColumnName).ToArray(); sb.AppendLine(string.Join(",", columnNames)); foreach (DataRow row in dt.Rows) { var fields = row.ItemArray.Select(field => field.ToString()).ToArray(); sb.AppendLine(string.Join(",", fields)); } File.WriteAllText(fileName, sb.ToString(), Encoding.UTF8);