如何将 IOrderedEnumerable转换为到 PagedList它使用 OrderBy 和 ThenBy？
假设您有一个 Product 类，其成员被声明为嵌套类型 ProductFeature:
public class Product {
public ProductFeature ProductID {get;set;}
public ProductFeature ProductName {get;set;}
}
public class ProductFeature {
public int FeatureID {get;set;}
public string FeatureName {get;set;}
}
并且您有一个方法将所有产品加载为 PagedList:
var list = db.GetProductList();//returns PagedList<Product>:
现在您想要过滤并应用一些 < code>OrderBy 和 ThenBy：
var sorted = model.Products.OrderBy(x => x.ProductName).ThenBy(x=>x.ProductID);
排序的结果可以视为 IEnumerable 并且也IOrderedEnumerable。
问题是当我们尝试将 sorted 转换回 PagedList 或 List 时。
base {System.SystemException}: {"At least one object must implement IComparable."}
Message: "At least one object must implement IComparable."
有什么方法可以将 sorted 再次转换为 List 吗？
suppose you have a class Product, with members that are declared as nested type ProductFeature:
public class Product {
public ProductFeature ProductID {get;set;}
public ProductFeature ProductName {get;set;}
}
public class ProductFeature {
public int FeatureID {get;set;}
public string FeatureName {get;set;}
}
and somewhere you have a method to load all products as a PagedList<Product>:
var list = db.GetProductList();//returns PagedList<Product>:
now you want to filter and apply some OrderBy and ThenBy:
var sorted = model.Products.OrderBy(x => x.ProductName).ThenBy(x=>x.ProductID);
the result of sorted can be treated as IEnumerable<T> and also IOrderedEnumerable<T>.
the problem is when we try to convert sorted back to PagedList<Product>, or List<Product>.
base {System.SystemException}: {"At least one object must implement IComparable."}
Message: "At least one object must implement IComparable."
Any way to convert sorted as a List again?
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评论（1）
您的第一个问题是
Product.ProductName和Product.ProductID是ProductFeature的实例，它没有实现IComparable和因此，当您尝试枚举sorted的结果时，您的OrderBy和ThenBy会失败。这显然是异常消息告诉您的内容。您的第二个问题是，当您说“将
sorted转换回PagedList或List时，您没有告诉我们“转换”的含义。 ;产品>。”但是，我怀疑您的意思实际上可以通过创建实现IComparable的实例来解决。Your first problem is that
Product.ProductNameandProduct.ProductIDare instances ofProductFeaturewhich does not implementIComparableand therefore yourOrderByandThenByfail when you try to enumerate over the results ofsorted. This is clearly what the exception message is telling you.Your second problem is that you didn't tell us what you mean by "convert" when you say "convert
sortedback toPagedList<Product>, orList<Product>." However, I suspect whatever you mean will actually be resolved by makingProductNameandProductIDinstances of something that implementIComparable.