如果选择的值为null,如何使Linq选择返回值？

Question

我有以下代码:

    [DisplayName("Created")]
    [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")]
    public DateTime? Created { get; set; }

    [DisplayName("Modified By")]
    public string ModifiedBy { get; set; }

    [DisplayName("Modified")]
    [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")]
    public DateTime? Modified { get; set; }

        from d in data
        select new Content.Grid
        {
            PartitionKey = d.PartitionKey,
            RowKey = d.RowKey,
            Order = d.Order,
            Title = d.Title,e
            Created = d.Created,
            CreatedBy = d.CreatedBy,
            Modified = d.Modified,
            ModifiedBy = d.ModifiedBy
        };

还有一个可能性d.Created,d.CreatedBy,d.Modified并且d.ModifiedBy可以为null.

我怎样才能让这个如果他们是null,则选择回到n/a了CreatedBy和ModifiedBy返回日期January, 1, 2012为Created和Modified？

Answer 1

您可以使用null-coalescing operator(??)为可为空的值类型或引用类型提供默认值:

from d in data
select new Content.Grid
{
    PartitionKey = d.PartitionKey,
    RowKey = d.RowKey,
    Order = d.Order,
    Title = d.Title,e
    Created = d.Created ?? new DateTime(2012,1,1),
    CreatedBy = d.CreatedBy ?? "n/a",
    Modified = d.Modified ?? new DateTime(2012,1,1),
    ModifiedBy = d.ModifiedBy ?? "n/a"
};