无法列出清单

Question

我在下面的行中收到错误.

 temp.day1_veh_p = string.Join(Environment.NewLine, day1.Where(x => x.plannedTriips == 1).Select(x => new {value=x.vehicleNumber+":"+x.shiftCompletedOn }).Cast<string>().ToArray());

错误消息正在发送

Unable to cast object of type '<>f__AnonymousType0`1[System.String]' to type 'System.String'.

列表day1是类型

public class tripDetails
{
    public string accountID { get; set; }
    public string supplierName { get; set; }
    public string supplierCode { get; set; }
    public DateTime shiftFrom { get; set; }
    public DateTime shiftTo { get; set; }
    public int plannedTriips { get; set; }
    public int actualTrips { get; set; }
    public DateTime forDate { get; set; }
    public string vehicleNumber { get; set; }
    public string shiftCompletedOn { get; set; }
    public class Comparer : IEqualityComparer<tripDetails>
    {
        public bool Equals(tripDetails x, tripDetails y)
        {
            return x.supplierCode == y.supplierCode;
        }

        public int GetHashCode(tripDetails obj)
        {
            return (obj.supplierCode).GetHashCode();
        }
    }
}

我究竟做错了什么？

Answer 1

问题是 new { value = ... }

更换:

Select(x => new {value=x.vehicleNumber+":"+x.shiftCompletedOn }).Cast<string>()

同

Select(x => x.vehicleNumber+":"+x.shiftCompletedOn)

你排序了.你根本不需要它Cast<string>().

您的原始代码为每个记录创建一个匿名类型的新实例,该实例具有一个value使用所需字符串调用的成员; 第二个版本只是创建字符串.

在某种程度上,尝试这个没有什么不同:

class Foo
{
    public string Bar {get;set;}
}
...
var foo = new Foo { Bar = "abc" };
string s = (string)foo; // doesn't compile

Answer 2

是的,匿名类型不是字符串,所以替换它

 .Select(x => new { value = x.vehicleNumber + ":" + x.shiftCompletedOn })

同

 .Select(x => x.vehicleNumber + ":" + x.shiftCompletedOn)

然后您可以使用查询(您不需要创建新数组)string.Join.

使用多行也很有帮助,它使您的代码更具可读性:

var vehicles = day1.Where(x => x.plannedTriips == 1)
              .Select(x => x.vehicleNumber + ":" + x.shiftCompletedOn);
string str = string.Join(Environment.NewLine, vehicles);