Writing CSV

CsvWriter.WriteRowAsync writes one row. Values that contain the separator, the quote character or a line break are quoted:

using var writer = new StringWriter();
var csvWriter = new CsvWriter(writer)
{
    EndOfLine = "\n", // Environment.NewLine by default
};

await csvWriter.WriteRowAsync("Name", "Age", "City");
await csvWriter.WriteRowAsync("Alice", "30", "New York");
await csvWriter.WriteRowAsync("Bob", "25", "London, UK");

Assert.Equal("Name,Age,City\nAlice,30,New York\nBob,25,\"London, UK\"", writer.ToString());

There is no header option: the header is the first row you write.

Quoting

The writer quotes a value when it contains the quote character, the separator, \r, \n, or a character of EndOfLine. Inside a quoted value, each quote character is doubled. Other values are written as they are. null and the empty string are both written as nothing:

using var writer = new StringWriter();
var csvWriter = new CsvWriter(writer) { EndOfLine = "\n" };

await csvWriter.WriteRowAsync("plain", "with,comma", "with \"quotes\"", "two\nlines", null, "");

Assert.Equal(""""
    plain,"with,comma","with ""quotes""","two
    lines",,
    """", writer.ToString(), ignoreLineEndingDifferences: true);

CsvReader reads these values back as they were written, except null, which is read back as an empty string.

Separators

Separator is , by default. Use ;, \t or any other character:

using var writer = new StringWriter();
var csvWriter = new CsvWriter(writer)
{
    Separator = ';',
    EndOfLine = "\n",
};

await csvWriter.WriteRowAsync("Column1", "Column2");
await csvWriter.WriteRowAsync("Value1", "Value2");

Assert.Equal("Column1;Column2\nValue1;Value2", writer.ToString());

Read the data with the same Separator and Quote as it was written with.

Line terminators

EndOfLine is written between rows, and is Environment.NewLine by default, so the output depends on the operating system. Set it to produce the same output everywhere, for instance "\r\n" as RFC 4180 asks, or "\n". The writer does not write a line terminator after the last row.

Write a row value by value

When the values of a row come one at a time, call BeginRowAsync, then WriteValueAsync for each value, or WriteValuesAsync for several:

using var writer = new StringWriter();
var csvWriter = new CsvWriter(writer)
{
    EndOfLine = "\n",
};

await csvWriter.BeginRowAsync();
await csvWriter.WriteValueAsync("First");
await csvWriter.WriteValueAsync("Second");
await csvWriter.WriteValueAsync("Third");

await csvWriter.BeginRowAsync();
await csvWriter.WriteValuesAsync("Fourth", "Fifth", "Sixth");

Assert.Equal("First,Second,Third\nFourth,Fifth,Sixth", writer.ToString());

BeginRowAsync writes the line terminator that ends the previous row. WriteRowAsync is BeginRowAsync followed by WriteValuesAsync. Both also accept an IEnumerable<string?>.

Disable quoting

Set Quote to null to write every value as it is, without quoting or escaping:

using var writer = new StringWriter();
var csvWriter = new CsvWriter(writer)
{
    Quote = null, // Disable quoting (values won't be escaped)
};

await csvWriter.WriteRowAsync("A\"", "B");

Assert.Equal("A\",B", writer.ToString());

The output is then only valid when no value contains the separator or a line break: the writer does not check.

Flushing

The writer writes to the TextWriter as you go and never flushes or disposes it. Dispose the TextWriter, or call its FlushAsync, once the last row is written; see Write a file.