Obtain first string in an array which is not null using LINQ?

Question

I have a string array and I need to use the first string in the string array which is not null. Lets consider this code snippet -

string[] strDesc = new string[] {"", "", "test"};

foreach (var Desc in strDesc)
{
      if (!string.IsNullOrEmpty(Desc))
      {
           txtbox.Text = Desc;
           break;
      }
}

So, according to this code snippet, txtbox should now display "test".

To do this I have this code. This is working fine. But, I want to know if it is possible to use LINQ to obtain the same result and perhaps skip using an extra foreach loop?

Resharper is very helpful in such situations as it can tell when the loop can be converted to Linq and can actually convert it too. — Giorgi
– Giorgi, Commented Nov 10, 2010 at 9:02

Klaus Byskov Pedersen · Accepted Answer · 2010-11-10 08:59:01Z

11

You can do it like this:

var result = strDesc.First(s => !string.IsNullOrEmpty(s));

Or if you want to set it directly in the textbox:

txtbox.Text = strDesc.First(s => !string.IsNullOrEmpty(s));

Mind you that First will throw an exception if no string matches the criteria, so you might want to do:

txtbox.Text = strDesc.FirstOrDefault(s => !string.IsNullOrEmpty(s));

FirstOrDefault returns null if no element mathces the criteria.

answered Nov 10, 2010 at 8:59

Klaus Byskov Pedersen

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1 Comment

leppie Over a year ago

OrDefault, incase there are no null strings.

Marc Gravell · Accepted Answer · 2010-11-10 09:20:29Z

8

Just an interesting alternative syntax, to show that you don't always need lambdas or anonymous methods to use LINQ:

string s = strDesc.SkipWhile(string.IsNullOrEmpty).First();

answered Nov 10, 2010 at 9:20

Marc Gravell

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3 Comments

pavanred Over a year ago

First() throws an exception if strDesc contains only nulls. So, FirstOrDefault() can be used instead.

Marc Gravell Over a year ago

@Pavanred - yes I am aware of that, but you didn't define what behaviour you wanted if nothing was found. And since the question seems to expect at least one, throwing an exception may be the correct thing to do.

pavanred Over a year ago

Yes, Of Course, Thanks. I noticed this when I tried it out and thought it would be good to share.

Preet Sangha · Accepted Answer · 2010-11-10 09:00:27Z

1

in .net 4.0 you can use IsNullOrWhiteSpace, but in earlier versions you need IsNullOrEmpty

string desc = strDec.Where(s => !string.IsNullOrWhitespace(s))
                       .FirstOrDefault() ?? "None found";
txtBox.Text = desc;

answered Nov 10, 2010 at 9:00

Preet Sangha

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