问题
How to make LINQ case sensitive and NOT case sensitive depending on the situation?
I'm using sql server 2008 and Entity Framework 4.0.
I changed the COLLATION to make SQL Server case sensitive. so that for scenarios like these:
query = query.Where(x => x.Username == username);
it works great. However I need to be able to pull out data from db ignoring case when searching by subject (or name or similar) like so:
query = query.Where(x => (x.Name.Contains(Name)));
which doesn't work when record is "TestString" and i'm looking for "test" or "Test" or similar. How would i make it so that when it would find a text or part of a string in a text? thanks
回答1:
LINQ has no concept of case sensitivity, it only cares about boolean evaluation. So if you want to ignore case, you should do something like:
query = query.Where(x => (x.Name.ToLower().Contains(Name.ToLower())));
Chances are you will want to pass a CultureInfo to ToLower() (or use ToLowerInvariant()), and you might want to cache the result of Name.ToLower() so as to not have to perform that operation a potentially large number of times, but this should get you started.
回答2:
query = query.Where(x => string.Equals(x.Name, Name, StringComparison.CurrentCultureIgnoreCase));
回答3:
Read my reply to this:
String.Equals() not working as intended
It isn't the reply you wanted, probably :-)
Ah... and if you have to convert to the same case to make comparisons, ToUpper is better than ToLower. Don't ask me why. But you can read here: Case insensitive string compare in LINQ-to-SQL
回答4:
Queryable.Contains has an overload taking an IEqualityComparer<T> used for comparision. See msdn. If you supply a case insensitive comparer, this should work - I'm quite sure there is one in the framework already.
来源：https://stackoverflow.com/questions/5104520/linq-case-sensitive