using System.Net.Http.Formatting;

​

public class ProductCsvFormatter : BufferedMediaTypeFormatter 

{

    public override bool CanWriteType(System.Type type)

    {

        if (type == typeof(Product))

        {

            return true;

        }

        else

        {

            Type enumerableType = typeof(IEnumerable<Product>);

            return enumerableType.IsAssignableFrom(type);

        }

    }

    public override bool CanReadType(Type type)

    {

            return false;

    }

    public override void WriteToStream(Type type, object value, Stream writeStream, HttpContent content)

    {

        using (var writer = new StreamWriter(writeStream))

        {

            var products = value as IEnumerable<Product>;

            if (products != null)

            {

                foreach (var product in products)

                {

                    WriteItem(product, writer);

                }

            }

            else

            {

                var singleProduct = value as Product;

                if (singleProduct == null)

                {

                    throw new InvalidOperationException("Cannot serialize type");

                }

                WriteItem(singleProduct, writer);

            }

        }

    }

    // Helper methods for serializing Products to CSV format.

    private void WriteItem(Product product, StreamWriter writer)

    {

        writer.WriteLine("{0},{1},{2},{3}", Escape(product.Id),

            Escape(product.Name), Escape(product.Category), Escape(product.Price));

    }

    static char[] _specialChars = new char[] { ',', '\n', '\r', '"' };

    private string Escape(object o)

    {

        if (o == null)

        {

            return "";

        }

        string field = o.ToString();

        if (field.IndexOfAny(_specialChars) != -1)

        {

            // Delimit the entire field with quotes and replace embedded quotes with "".

            return String.Format("\"{0}\"", field.Replace("\"", "\"\""));

        }

        else return field;

    }

​

​

​

​

}

​