String.IsNullOrEmpty in LINQ To SQL query?

Question

My DBML exposes a record set that has a nullable nvarchar field. This nullable nvarchar field is represented as a string in my C# code.

Sometimes this field is null, sometimes it is an empty string, and sometimes it actually has a value.

Does String.IsNullOrEmpty() work in LINQ To SQL? For instance, would the following work:

var results = from result in context.Records
              where String.IsNullOrEmpty(result.Info) == false
              select result;

You can try, LinqPad is your firend. (http://www.linqpad.net/) — moi_meme, Nov 08 '11 at 18:04
duplicate of http://stackoverflow.com/questions/1368946/linq-syntax-where-string-value-is-not-null-or-empty — hatchet - done with SOverflow, Nov 08 '11 at 18:05

user7116 · Accepted Answer · 2011-11-08T18:09:59.243

54

Curiously, per MSDN String.IsNullOrEmpty is supported (by virtue of it not being unsupported), yet I can only find complaints about it not being supported.

However, if it does work you should not explicitly compare it to a boolean value, instead:

var results = from result in context.Records
          /*XXX broke :( where !String.IsNullOrEmpty(result.Info) */
          where !(result.Info == null || result.Info.Equals(""))
          select result;

edited Nov 08 '11 at 18:09

answered Nov 08 '11 at 17:59

user7116

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That didn't worked for me. Profiler showed only check for empty string, but not for `null` value. – Johnny_D Mar 06 '14 at 09:35

score 26 · Answer 2 · answered Nov 08 '11 at 18:01

26

I don't know if that works, but I'm sure this does:

where (result.Info ?? "") != ""

(strongly recommend the parens, query generator can get confused without them)

answered Nov 08 '11 at 18:01

Amy B

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I like this one, but I guess much like `String.IsNullOrEmpty` being not supported without documentation to that effect the [null coalesce operator is supported without documentation](http://msdn.microsoft.com/en-us/library/bb882653.aspx)! Oy. – user7116 Nov 08 '11 at 18:13
Worked for me, but is this style of coding OK? – Yeheshuah May 18 '21 at 08:39

score 10 · Answer 3 · answered Nov 08 '11 at 18:09

It is not supported since attempting to use it results in a NotSupportedException being thrown with this message:

Method 'Boolean IsNullOrEmpty(System.String)' has no supported translation to SQL.

Instead, you can use this approach to do the same thing:

var results = from result in context.Records
              where result.Info != null && result.Info.Length > 0
              select result;

You may also use result.Info != String.Empty instead of checking the length. Both approaches will work.

score 3 · Answer 4 · answered Dec 17 '18 at 19:16

3

I had problems with all answers except for @ahmad-mageed's answer.

Ended up using a more concise syntax of:

where (result.Info ?? "").Length > 0

Or

result => (result.Info ?? "").Length > 0

answered Dec 17 '18 at 19:16

Robert J. Good

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score 0 · Answer 5 · answered Apr 04 '19 at 09:05

You can use a function as argument to the Where method if you use a Linq query, e.g.

var results = context.Records.Where(string.IsNullOrEmpty);

But in this case that would give you all null or empty elements, instead of the opposite. Then create an extension method to the string class (e.g. string.IsNotNullOrEmpty) or do something like this:

var results = context.Records.Except(context.Records.Where(string.IsNullOrEmpty));

String.IsNullOrEmpty in LINQ To SQL query?

5 Answers5