ASP.NET WebAPI导出CSV

以下是ASP.NET WebAPI导出CSV的完整攻略：

一、添加CSV文件支持

1. 首先，在WebApiConfig.cs文件中注册CSV输出格式，代码如下：

public static void Register(HttpConfiguration config)
{
    var csvFormatter = new CsvMediaTypeFormatter();
    config.Formatters.Insert(0, csvFormatter);

    //其他配置
}

1. 接下来，创建一个自定义的CSV媒体格式化器。该格式化器继承自MediaTypeFormatter。

public class CsvMediaTypeFormatter : MediaTypeFormatter
{
    public CsvMediaTypeFormatter()
    {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/csv"));
    }

    public override bool CanWriteType(Type type)
    {
        if (type == null)
            throw new ArgumentNullException(nameof(type));

        return IsTypeOfIEnumerable(type);
    }

    private bool IsTypeOfIEnumerable(Type type)
    {
        return type.GetInterfaces().Any(t => t == typeof(IEnumerable));
    }

    public override Task WriteToStreamAsync(Type type, object value,
        Stream stream, HttpContent content, TransportContext transportContext)
    {
        return Task.Factory.StartNew(() => WriteToStream(type, value, stream));
    }

    private void WriteToStream(Type type, object value, Stream stream)
    {
        StringWriter writer = new StringWriter();
        writer.WriteLine("\"" + string.Join("\",\"", type.GetProperties().Select(p => p.Name)) + "\"");

        foreach (var obj in (IEnumerable<object>)value)
        {
            var vals = obj.GetType().GetProperties().Select(prop => new {
                Value = prop.GetValue(obj, null)
            }).Select(v => v.Value.ToString());

            var line = string.Join(",", vals);
            writer.WriteLine(line);
        }

        var streamWriter = new StreamWriter(stream);
        streamWriter.Write(writer.ToString());
        streamWriter.Flush();
    }
}

二、使用CSV文件导出数据

以下是两个示例：

1. 导出实体数据

[HttpGet]
[Route("api/Orders/Export")]
public HttpResponseMessage ExportData()
{
    var orderQuery = db.Orders.Where(x => x.Status == OrderStatus.Shipped);

    //这里省略了Order实体的具体定义

    var orders = orderQuery.ToList();

    var response = new HttpResponseMessage(HttpStatusCode.OK);
    response.Content = new ObjectContent<List<Order>>(orders, new CsvMediaTypeFormatter());

    response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
    {
        FileName = "Orders.csv"
    };

    return response;
}

1. 导出自定义数据

[HttpGet]
[Route("api/Customers/Export")]
public HttpResponseMessage ExportData()
{
    var customerQuery = db.Customers.Where(x => x.IsVIP);

    var customers = customerQuery.ToList().Select(c => new {
        Name = c.Name,
        Gender = c.Gender == Gender.Male ? "男" : "女",
        City = c.Address.City,
        Province = c.Address.Province
    });

    var response = new HttpResponseMessage(HttpStatusCode.OK);
    response.Content = new ObjectContent<IEnumerable>(customers, new CsvMediaTypeFormatter());

    response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
    {
        FileName = "Customers.csv"
    };

    return response;
}

以上就是ASP.NET WebAPI导出CSV的完整攻略，具体实现还需要根据项目需求进行调整。