C# Linq .Select(int.parse) on empty array results in “Input string was not in a correct format”

Question

I have the following line of code:

List<int> _people = code.data.loadScalarDataPoint(code.enums.pathNames.Department, "Department_Staff", RecId).Split('|').Select(int.Parse).ToList();

The static method loadScalarDataPoint returns a string of the selected column for given inputs.

In this instance, it returns a list of pipe delimited integers (eg 12|45|88|1543|123 ) or if the column is NULL it will return an empty string.

Using the linq Select(int.Parse) works if there is a result but without it throws the following error " Input string was not in a correct format "

I know why, as you can't parse an empty string into a int , however is there a way within the single line of code to check for this?

Or do I need to get the result into a string, check if it has contents and if so parse into a list of int s?

Answer 1

EDIT with full explanation: In your failing case, the loadScalarDataPoint method returns an empty string, which the call to Split(',') returns an IEnumerable<String> with one empty string in it. The call to Select(Int32.Parse) throws an exception because an empty string is not in the correct format.

Use

.Split(new [] {'|'}, StringSplitOptions.RemoveEmptyEntries)

Answer 2

为什么不先检查非空结果？

List<int> _people = code.data.loadScalarDataPoint(code.enums.pathNames.Department, "Department_Staff", RecId).Split('|').Where(a => a.Any()).Select(int.Parse).ToList();

Answer 3

Add the following before the select:

.Where(x=>!string.IsNullOrEmpty(x))

This basically ensures that when doing the select there are only elements that have a string value.

Be aware you will need to handle the empty case.