CODEWITHSUNDEEP
c#arrayslinqexpression
MegaMark
MegaMark

Reputation: 610

lambda expressions for comparing whether or not a string[] contains a given string

My project was working just fine until I had to account for an array of strings and not just one... I don't know how to fix this. The Country is a property of the current class this method is in. It used to be a single string but now is an array.

Originally it looked like this:

private Expression<Func<Payment, bool>> CountryMatches()
{
   if (Country.Length < 1) return Skip;
   return payment => payment.Country.ToLower().Contains(Country.ToLower());
}

What I can't figure out is how to set it up so that if ANY of the strings in Country match payment.Country... and of course this is passing back an expression... This is my best guess (but obviously not correct) of how to do what I need to do:

private Expression<Func<Payment, bool>> CountryMatches()
{
   if (Country.Length < 1) return Skip;
   return payment => payment.Country.ToLower() == Country.Any().ToLower();
}

Upvotes: 1

Views: 2381

Answers (2)

Jon
Jon

Reputation: 437494

You want to check all the contents of Country against payment.Country, like this:

return payment => Country.Any(
    c => payment.Country.ToLower().Contains(c.ToLower()));

That said, this is a rather bad way to check if one string is a substring of another mainly because it does a lot of unnecessary work by converting to lowercase again and again. Here's a better way to do it:

return payment => Country.Any(
    c => payment.Country.IndexOf(c, StringComparison.OrdinalIgnoreCase) >= 0);

Upvotes: 6

David
David

Reputation: 10708

.Any Takes a lambda in, which can perform your comparison. The above code assums it returns some object which equates to true when compared, but Any returns a simple bool. Thus, try

return payment =>
    Country.Any(c =>
        string..Equals(payment.Country, c, StringComparison.InvariantCultureIgnoreCase));

Also note that .Equals is often preferable to the "==" operator, particularly with strings, wherin you can pass the StringComparison parameter.

Upvotes: 2

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