连接对象数组的字段值

Question

private readonly List<A> _previousDayPrices;    

private void PrintDebugPreviousDayPrice(DateTime date)
{
    var str = "";
    foreach (var d in _previousDayPrices.Take(2))
    {
        str += d.Price;
        str += "-";
        str += d.Date;
        str += "-";
        str += d.EuroExchangeRateDate;
        str += "-";
        str += d.EuroExchangeRate;
        str += ",";
    }
}

What is the linq manner to do this or is there a string's method ?

Answer 1

像这样尝试linq：

string.Join(",", this._previousDayPrices.Take(2).Select(d => string.Format("{0}-{1}-{2}-{3}", d.Price, d.Date,d.EuroExchangeRateDate, d.EuroExchangeRate)).ToArray());

Answer 2

That's the way your code may be improved

private readonly List<AnItemType> _previousDayPrices;
private void PrintDebugPreviousDayPrice(DateTime date)
{
    StringBuilder stringBuilder = new StringBuilder();
    foreach (AnItemType item in _previousDayPrices)
    {
        String valueToAppend = String.Format(
            "{0}-{1}-{2}-{3},",
            item.Price,
            item.Date,
            item.EuroExchangeRateDate,
            item.EuroExchangeRate);
        stringBuilder.Append(valueToAppend);
    }
}

Answer 3

Try

        var result = string.Join(",", (from d in _previousDayPrices.Take(2) select 
               string.Join("-", {d.Price, 
                                 d.Date, 
                                 d.EuroExchangeRateDate,
                                 d.EuroExchangeRate})).ToArray());

This assumes that Price, Date, EuroExchangeRateDate and EuroExchangeRate are already strings (I doubt that based upon their names, but your sample points in this direction). If not, you need to convert them before.

Answer 4

Try it ,

var res = _previousDayPrices.Take(2).Aggregate((i,j) => i.Price + "-" + i.Date + "-" + i.EuroExchangeRateDate +"-" + i.EuroExchangeRate + "," + 
        j.Price + "-" + j.Date + "-" + j.EuroExchangeRateDate +"-" + j.EuroExchangeRate +
        )