CS0029 C＃无法将类型隐式转换为'string []'

Question

I'm have initialised a string array,then inside a foreach loop I try to execute a linq query and store the result of the query to the string array that was initialised.

I tried ToList() and such but it does'nt work

public class TierImaegeDefinitionDTO
        {
            public string Tier { get; set; }
            public string[] ImageDefinition { get; set; }
        }
foreach (var tierVal in tierList)
{
                String tier = tierVal.Tier;
                 var imageDefinitionList = (from p in _context.Product
                                            join ti in _context.TierImageMap 
                                            on p.Id equals ti.ProductId join t 
                                            in _context.Tiers on ti.TierType 
                                            equals t.Id
                                           where (p.Id == ProductId) && 
                                           (t.TierType == tier)
                                             select new
                                           {
                                               ti.ImageName,

                                           }).ToList().Distinct();
await _context.SaveChangesAsync();

                tierVal.ImageDefinition = imageDefinitionList;//getting error in this line
            }

Answer 1

ImageDefinition is an array of string[]. ToList() will return List<T>, and Distinct will return IEnumerable<T>. You need to change your call so that it ends with

.Distinct().ToArray()

Another problem is that you are selecting an object, so your .ToList() is actually returning List<anonymous type>. Instead, you can just select ti.ImageName

var imageDefinitionList = 
    (from p in _context.Product 
        join ti in _context.TierImageMap on p.Id equals ti.ProductId 
        join t in _context.Tiers on ti.TierType equals t.Id 
        where (p.Id == ProductId) && (t.TierType == tier) 
        select ti.ImageName
    ).Distinct().ToArray();