使用 Linq c# 检查值是否在列表中

Question

I have a List public static List<string> HandledErrorCodes { get; } = new List<string> {... public static List<string> HandledErrorCodes { get; } = new List<string> {... with some data inside. And i need to check, if a value ( ex.ErrorCode ) is inside this list. I thing the best way is with Linq:

if ((exception is DomainException ex 
    && CommandTriggerCommon.HandledErrorCodes.Any(ex.ErrorCode))

But i'm getting an error "Argument 2: cannot convert from 'string' to 'System.Func<string, bool>'". What is the best way to do that?

Answer 1

Use List.Contains() to find if an element exists, not Any :

if ((exception is DomainException ex 
    && CommandTriggerCommon.HandledErrorCodes.Contains(ex.ErrorCode))

If you insist on using LINQ (why?) you need to specify the condition as a Func<T,bool>

if ((exception is DomainException ex 
    && CommandTriggerCommon.HandledErrorCodes.Any(e=>e==ex.ErrorCode))

Both methods will iterate over the entire list to find matches. If you have more than a few dozen error codes you can speed this up by using a HashSet instead of a List<string> . HashSet.Contains will be far faster than a linear search as the number of items grows.

Answer 2

Any takes Func<T,bool> (or in your specific case Func<string,bool> ) - you're passing it just a string

It should be ... && CommandTriggerCommon.HandledErrorCodes.Any(ec => ec == ex.ErrorCode)