Sequence不包含匹配的元素

Question

我有一个子类别模型在mvc 4应用程序的衬衫店，我想使用种子数据填充数据库时，我运行我的应用程序，我收到错误消息:"序列包含不匹配的元素"

我代码:

    var subCategories = new List<SubCategory>
        {
    new SubCategory{Category = categories.Single(s => s.Name == "Animals") , Name "Animal Prints"},
    new SubCategory{Category = categories.Single(s => s.Name == "Animals") , Name = "Bugs"},
        };

Answer 1

原因是您的类别中没有任何名称为"Animals"的条目。如果你想检查

   var categorie = categories.where(s => s.Name == "Animals").SingleOrDefault();
   if(categories == null)
   {
     // db is not seeded with categories do something
   }
   else
   {     
        var subCategories = new List<SubCategory>
        {
           new SubCategory{Category = categorie  , Name "Animal Prints"},
           new SubCategory{Category = categorie  , Name = "Bugs"},
        };
   }