I am using LINQ to search through one of my Entity Framework tables and find a "group" based on the name. The name is a string and appears to be Unicode (says it is in the edmx). I have a method GetGroup()
and I pass in a name to search for. Debugging through the code, I already have a group named "Test" in my database. Once I pass in a group named "TEST" I expect it to return the "Test" which was already in the database. It for some reason, does not find the "Test" and thinks "TEST" doesn't exist. Here is my query, I cannot see why it does not work. Please help.
"name" is the passed in the group name. My .Equals
seems to only work if the gr.Name
and name are the exact same. If one character is capital in one of the two strings, then the .Equals doesn't work. I have tried to use InvariantCultureIgnoreCase
, and that did not seem to help. In case someone asks, the MyLeagueId
and LeagueId
will always match, the database is setup so there can be a group in a different league id. I do not think this is the problem.
Group g = (from gr in this.DatabaseConnection.Groups
where gr.Name.Equals(name, StringComparison.OrdinalIgnoreCase) &&
gr.LeagueId == this.MyLeagueId
select gr).FirstOrDefault();
You should not use == (equality operator) to compare these strings because they compare the reference of the string, i.e. whether they are the same object or not. On the other hand, equals() method compares whether the value of the strings is equal, and not the object itself.
== compares the exact values. So it compares if the primitive values are the same, or if the references (addresses) are the same. That's why == often doesn't work on Strings; Strings are objects, and doing == on two string variables just compares if the address is same in memory, as others have pointed out. .
In String, the == operator is used to comparing the reference of the given strings, depending on if they are referring to the same objects. When you compare two strings using == operator, it will return true if the string variables are pointing toward the same java object. Otherwise, it will return false .
The string comparison with StringComparison.OrdinalIgnoreCase
works in memory or with IEnumerable<T>
. You are trying to use it with IQueryable<T>
, but the provider of your queryable does not understand it.
This works for me:
db.Users.FirstOrDefault(
s => s.Username.Equals(username, StringComparison.OrdinalIgnoreCase)
);
When using LINQ to Entities, it will automatically convert it to LINQ to SQL. And if the database field you are doing a .Equals on does not have a collate of NOCASE (SQLite in my example) then it will always be case-sensitive. In otherwords, the database defines how to do the string comparison rather than code.
Use the String.Compare()
as it can be translated to Sql.
Here are some examples of string matching in Linq, with the Sql translation as well.
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