Entity Framework behavior with Whitespaces

Question

I have a scenario where I need to allow empty duplicates and reject other kinds of duplicates so I am checking for existing records before inserting a new one using the following query.

this.dbContext.Employees.FirstOrDefault(t =>!string.IsNullOrEmpty(t.Name) && !string.IsNullOrEmpty(newRecord.Name) && t.Name.Trim().Equals(newRecord.Name.Trim(), StringComparison.InvariantCultureIgnoreCase));

The thing is that when I have data like following:

oldRecord.Name="   "

newRecord.Name="   "

The above query returns Null. which is weird because

1. result of .string.IsNullOrEmpty(" ") is true
2. result of " ".Trim().Equals(" ".Trim(), StringComparison.InvariantCultureIgnoreCase) is true

So the above query should give me results.

Any idea why I am getting this behavior? and will the above query be evaluated client side?

Answer 1

For that there's another method called IsNullOrWhiteSpace , which has "broader" application and works as you expect:

var whiteSpaceStrings = new string[]
{
    "   ", // some spaces
    "           ", // some tabs
    string.Empty, // empty
    "", // empty
};
foreach (var str in whiteSpaceStrings)
{
    Console.WriteLine(string.IsNullOrWhiteSpace(str));
}

It prints all true :)

Answering your doubts: IsNullOrEmpty checks if string is null or empty - but empty string is string without any character. And whitespace (any) is character itself:)