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 += ",";
    }
}

执行此操作的linq方式是什么，或者是否有字符串的方法？

Answer 1

尝试这样的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

这是您的代码可以改进的方式

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

尝试

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

这假设Price，Date，EuroExchangeRateDate和EuroExchangeRate已经是字符串（我怀疑这是基于他们的名字，但你的样本指向这个方向）。如果没有，您需要先转换它们。

Answer 4

试试吧，

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

对象数组的concat字段值

4 个答案: