How to Efficiently Convert a DataTable to a CSV File in C#?

Conversion of DataTable to CSV in C#

When saving DataTable data to a CSV file, you may encounter issues with incorrect data separation. Solutions are provided below:

Consider the following code:

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)
{
    // ... (此处代码仅写入每一行的第一个单元格数据) ...
}

File.WriteAllText("test.csv", sb.ToString());

The CSV file created by the above code only contains data for the first cell of each row. To solve this problem, a more robust approach can be used:

.NET 3.5 and above

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 above

For .NET 4.0 and above, the code can be further simplified:

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());

Handling special characters

If you need to handle special characters (such as double quotes) in the data field, you can modify the loop block in the code:

foreach (DataRow row in dt.Rows)
{
    IEnumerable<string> fields = row.ItemArray.Select(field =>
        string.Concat("\"", field.ToString().Replace("\"", "\"\""), "\""));
    sb.AppendLine(string.Join(",", fields));
}

Additionally, to avoid large documents in memory, the CSV content can be written line by line instead of writing the entire document at once.

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