Performing a LINQ query with optional search clauses?

Use string. Equals: from p in People.All() where (firstname == null || string. Equals (firstname, p.

FirstName, StringComparison. InvariantCultureIgnoreCase)) && (lastname == null || string. Equals (lastname, p.

LastName, StringComparison. InvariantCultureIgnoreCase)) select p Not only does this avoid the null problem, but it forces you to specify a string comparison type (a good thing). In other words, you specify whether to use rules specific to the local or invariant culture when performing the case-insensitive comparison.

Just curious... – Josh E Aug 18 '10 at 16:32.

You don't need to call ToLower() use string. Compare instead with ignoreCase string. Compare(firstName, p.

FirstName, true).

Make sure it's not null before calling the ToLower: (firstname==null || (firstname! = null && firstname.ToLower()==p.FirstName.ToLower())).

It doesn't work when both are null because the first part of the statement will evaluate to true, disallowing short-circuiting of the evaluation. Why not use equivalency rules to flip the statement? (firstName!

= null && firstName.ToLower() == p.firstName.ToLower()) EDIT: I wrote the following up and ran it successfully in LINQPad 4, with no issues. I'm assuming that the call to People.All() simply returns an IQueryable with the full set of records? Maybe post your exception text here so we can see if there's something you've inadvertently missed?

Void Main() { string a = null; string be = null; var peeps = new List { new Person { FirstName = "John", LastName = "Connor" }, new Person { FirstName = "Sarah", LastName = "Connor", }, new Person { FirstName = "Cletus", LastName = "Handy" } }; var somePeeps = from p in peeps where (a == null || a.ToLower() == p.FirstName.ToLower()) && (b == null || b.ToLower() == p.LastName.ToLower()) select p; somePeeps.Dump(); } public class Person { public string FirstName { get; set;} public string LastName { get; set;} }.

If the first part is true, then it shouldn't evaluate the second part due to short-circuited OR though. – Earlz Jul 16 '10 at 18:07.

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