Question

我正在使用FileHelperAsyncEngine<T>类（来自FileHelpers NuGet package）从MVC应用程序流式传输非常大的CSV文件。

我们要将许多不同类型的数据传输到CSV，我正在寻找一种设置默认分隔符的方法，以避免使用[DelimitedRecord(",")]属性修饰我的数据类。

我知道我可以使用CsvEngine类，但性能至关重要，异步版本的速度要快几个数量级。

我是否遗漏了某些内容或无法设置默认记录分隔符？

Answer 1

我想毕竟有可能发生任何事情。这很难看，但是这个版本使用反射来创建一个带有属性的新代理类。

namespace FileHelpersConsoleApplication1
{
    public class Program
    {
        public class Record
        {
            public string Id;
            public string Name;
        }

        public static void Main(string[] args)
        {
            var type = typeof(Record);

            var defaultDelimiter = ",";

            var aName = type.Assembly.GetName();
            var ab = AppDomain.CurrentDomain.DefineDynamicAssembly(aName, AssemblyBuilderAccess.Run);
            var mb = ab.DefineDynamicModule(aName.Name);
            var tb = mb.DefineType(type.Name + "Proxy", TypeAttributes.Public, type);

            var attrCtorParams = new Type[] { typeof(string) };
            var attrCtorInfo = typeof(DelimitedRecordAttribute).GetConstructor(attrCtorParams);
            var attrBuilder = new CustomAttributeBuilder(attrCtorInfo, new object[] { defaultDelimiter });
            tb.SetCustomAttribute(attrBuilder);

            var newType = tb.CreateType();

            var engine = new FileHelperAsyncEngine(newType);
            //var options = engine.Options as DelimitedRecordOptions;
            //options.Delimiter = "|"; // you can still change delimiter if you need to

            string src = "abc,JohnDoe";
            using (engine.BeginReadString(src))
            {
                var enumerator = (engine as IEnumerable<object>).GetEnumerator();
                enumerator.MoveNext();

                var currentRecord = enumerator.Current as Record;
                Assert.AreEqual("abc", currentRecord.Id);
                Assert.AreEqual("JohnDoe", currentRecord.Name);
            }
            Console.ReadKey();
        }
    }
}

Answer 2

您可以将engine.Options转换为DelimitedRecordOptions并更改分隔符。像这样：

public class Program
{
    [DelimitedRecord(",")] // you need to specify some delimiter, even if you change it later...
    public class Record
    {
        public string Id;
        public string Name;
    }

    static void Main(string[] args)
    {
        var engine = new FileHelperAsyncEngine<Record>();
        var options = engine.Options as DelimitedRecordOptions;
        options.Delimiter = "|"; // change the delimiter to vertical bar

        // test
        string src = "abc|JohnDoe";
        using (engine.BeginReadString(src))
        {
            var enumerator = (engine as IEnumerable<Record>).GetEnumerator();
            enumerator.MoveNext();
            Assert.AreEqual("abc", enumerator.Current.Id);
            Assert.AreEqual("JohnDoe", enumerator.Current.Name);
        }
        Console.ReadKey();
    }
}

FileHelperAsyncEngine <t> - 设置默认分隔符？

2 个答案: