Question

我已经在我的asp.net mvc wen应用程序中定义了以下模型类： -

public class CustomerDetails
{
    public AccountDefinition AccountDefinition {get; set;}
    public SDOrganization SDOrganization {get; set;}
    public ICollection<SiteDefinition> SiteDefinition { get; set; }
    public ICollection<AaaPostalAddress> AaaPostalAddress { get; set; }
    public ICollection<AaaContactInfo> AaaContactInfo { get; set; }
    public virtual ICollection<UserSiteMapping> UserSiteMapping { get; set; } 
}

然后我写下面的查询： -

var customerDetails = entities.AccountDefinitions
    .Where(a => a.ORG_ID == id)
    .Select(cd => new CustomerDetails
    {
        AccountDefinition = cd,
        SDOrganization = cd.SDOrganization,
        AaaPostalAddress = cd.SDOrganization.AaaPostalAddresses,
        AaaContactInfo = cd.SDOrganization.AaaContactInfoes,
        SiteDefinition = cd.SiteDefinitions,
        UserSiteMapping = cd.SiteDefinitions.Select(p2 => p2.UserSiteMappings) //this is raising the exception
    })
    .SingleOrDefault();

return customerDetails;

但是我得到了以下误导性错误： -

无法隐式转换类型'System.Collections.Generic.IEnumerable＆gt;'到'System.Collections.Generic.ICollection'。存在显式转换（您是否错过了演员？）

我不确切知道导致错误的原因，因为我选择了与SiteDefinition相关的UserSiteMapping，并且我将这些分配给UserSiteMapping的集合（在我的视图模型中定义）??? ？

Answer 1

改为使用SelectMany：

UserSiteMapping = cd.SiteDefinitions.SelectMany(p2 => p2.UserSiteMappings)

您可能还需要ToList()或ToArray()来电从IEnumerable<T>切换到ICollection<T>：

UserSiteMapping = cd.SiteDefinitions.SelectMany(p2 => p2.UserSiteMappings).ToList()

无法隐式转换类型'System.Collections.Generic.IEnumerable

1 个答案: