C# Cannot use Linq DefaultIfEmpty in ushort list items?

Question

I want to take max value of ushort list and when that list is empty I want set "1" for default value.

For example:

List<ushort> takeMaxmumId = new List<ushort>();
var max = takeMaxmumId.Select(x=>x).DefaultIfEmpty(1).Max();

In my Example Visual Studio Show me this error:

'IEnumerable' does not contain a definition for 'DefaultIfEmpty' and the best extension method overload 'Queryable.DefaultIfEmpty(IQueryable, int)' requires a receiver of type 'IQueryable'

When my list type were int I have not any problem, What is this problem in ushort type? And how can I fix this with best way?

Answer 1

The problem is that Select produces an IEnumerable<ushort>, while DefaultIfEmpty supplies an int default. Hence, the types do not match.

You can fix this by forcing ushort type on the default:

var max = takeMaxmumId.Select(x=>x).DefaultIfEmpty<ushort>(1).Max();
//                    ^^^^^^^^^^^^^
//            This part can be removed

Demo.

You can also convert sequence elements to int:

var max = takeMaxmumId.Select(x => (int)x).DefaultIfEmpty(1).Max();