Linq to Objects - query objects for any non-numeric data - linq

Question

I am trying to write some logic to determine if all values of a certain property of an object in a collection are numeric and greater than zero. I can easily write this using ForEach but I'd like to do it using Linq to Object. I tried this:
var result = entity.Reports.Any(
x =>
x.QuestionBlock == _question.QuestionBlock
&& (!string.IsNullOrEmpty(x.Data)) && Int32.TryParse(x.Data, out tempVal)
&& Int32.Parse(x.Data) > 0);
It does not work correctly. I also tried this, hoping that the TryParse() on Int32 will return false the first time it encounter a string that cannot be parsed into an int. But it appears the out param will contain the first value string value that can be parsed into an int.
var result = entity.GranteeReportDataModels.Any(
x =>
x.QuestionBlock == _question.QuestionBlock
&& (!string.IsNullOrEmpty(x.Data)) && Int32.TryParse(x.Data, out tempVal));
Any help is greatly appreciated!

Answer 1

If you want to test if "all" values meet a condition, you should use the All extension method off IEnumerable<T>, not Any. I would write it like this:
var result = entity.Reports.All(x =>
{
int result = 0;
return int.TryParse(x.Data, out result) && result > 0;
});
I don't believe you need to test for an null or empty string, because int.TryPrase will return false if you pass in a null or empty string.

Answer 2

var allDataIsNatural = entity.Reports.All(r =>
{
int i;
if (!int.TryParse(r.Data, out i))
{
return false;
}
return i > 0;
});
Any will return when the first row is true but, you clearly say you would like to check them all.

Answer 3

You can use this extension which tries to parse a string to int and returns a int?:
public static int? TryGetInt(this string item)
{
int i;
bool success = int.TryParse(item, out i);
return success ? (int?)i : (int?)null;
}
Then this query works:
bool all = entity.Reports.All(x => {
if(x.QuestionBlock != _question.QuestionBlockint)
return false;
int? data = x.Data.TryGetInt();
return data.HasValue && data.Value > 0;
});
or more readable (a little bit less efficient):
bool all = entityReports
.All(x => x.Data.TryGetInt().HasValue && x.Data.TryGetInt() > 0
&& x.QuestionBlock == _question.QuestionBlockint);
This approach avoids using a local variable as out parameter which is an undocumented behaviour in Linq-To-Objects and might stop working in future. It's also more readable.