Question

string personName= "JoHn";  
//(in my table iam already having a person named='john')

Func<Person, bool> predicate = (p) => p.Name== personName;

var res2 = dataContext.Persons.Any(predicate);                //returns false
var res1 = dataContext.Persons.Any(p=>p.Name== personName);   // returns true

I think with predicate its considering case of personName property while without it its just ignoring case.

Any one know why??

Answer 1

A Func<Page, bool> is a delegate, which means you are running this in LINQ-to-Objects (i.e. in memory, in C#). .NET strings are case sensitive, so this will apply case.

This version, however:

var res1 = dataContext.Persons.Any(p=>p.Name== personName); 

is using IQueryable<T> and expression-trees; it will be executed as a TSQL filter, which will apply database rules. What happens here depends on how your DB is configured (it could be either case-sensitive or case-insensitive, depending on the database).

If you want them both to use the same logic, then note the difference here:

Expression<Func<Page, bool>> predicate = (p) => p.Name== personName;
var res2 = dataContext.Persons.Any(predicate);

The addition of Expression<...> makes this an expression-tree, not a delegate, so it is “composed” and executed at the database (via TSQL translation), exactly the same as:

var res1 = dataContext.Persons.Any(p=>p.Name== personName);