We are not sure if the input or the output is meant and has the value deleted. We also do see a different construct, not same to the above screenshots
We do feel that a proper requirement/value would speed up the answer. However, let’s start.
Regardless if there are some passing validations, we would state
- When using First/FirstOrDefault Linq Operator and passing some arguments on it (i+1).toString) it is against the defined method signature. We do see the complained string received, but lambda with Boolean output is expected
Legacy:
EDITED: Thanks to @supermanPunch for bringing the new feature into the picture (post below) 
vs. Windows:
-
Maybe the Idea was about returning a default string, when it is empty, which we can do with DefaultIfEmpty(“myString”)
[HowTo] LINQ - First Start # DefaultIfEmpty Operator -
the Split Function from the Strings ← was used:
Strings.Split(String, String, Int32, CompareMethod) Method (Microsoft.VisualBasic) | Microsoft Learn
where the split char can be optional, but we would assume a different goal was aimed
Example:
So more and more we risk drifting away from the needed output by the given input
Maybe you can elaborate more on what is given and what is needed. Thanks