String.Join method that ignores empty strings?

Question

The VB.NET method String.Join(separator, stringArray) is similar to PHP's implode, but any null elements in the array are replaced with an empty string, so thatc:

Dim myArray() as String = { "a", null, "c" }
Console.WriteLine(String.Join(", ", myArray));
// Prints "a, , c"

Is there a simple way to concatenate a set of strings with a separator that ignores empty strings?

I don't necessarily need to use arrays or String.Join or anything else. I just need the following transformations:

("a", "b", "c") --> "a, b, c"
("a", null, "c") --> "a, c"

As a completely different approach, it might be nice to not add null or empty strings to the array by creating an extension method .AddIfNotEmpty() — James Westgate
– James Westgate, Commented Feb 18, 2019 at 16:35
@JamesWestgate Whether that's a useful approach depends on the mechanism by which the array is populated and whether another part of the program is using the array. — Stewart
– Stewart, Commented Sep 18, 2020 at 13:11

KyleMit · Accepted Answer · 2022-06-24 21:09:56Z

232

VB.NET

String.Join(",", myArray.Where(Function(s) Not String.IsNullOrEmpty(s)))

C#

String.Join(",", myArray.Where(s => !string.IsNullOrEmpty(s)))

edited Jun 24, 2022 at 21:09

KyleMit♦

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answered May 1, 2013 at 20:36

Damith

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3 Comments

Doug Over a year ago

I'm getting an error: "'Where' is not a member of 'System.Array'". And I don't see anything about 'Where' on MSDN: msdn.microsoft.com/en-us/library/system.array.aspx

Doug Over a year ago

I had some luck with this instead: Array.FindAll(myArray, Function(s) Not String.IsNullOrEmpty(s)) Can you either change your answer or explain the Where statement?

Damith Over a year ago

Where method is from System.Linq, msdn.microsoft.com/en-us/library/bb534803.aspx

KyleMit · Accepted Answer · 2022-06-24 21:09:18Z

68

You can do it like this in CSharp:

String.Join(",", arr.Where(s => !String.IsNullOrEmpty(s)));

edited Jun 24, 2022 at 21:09

KyleMit♦

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answered Jan 8, 2015 at 9:40

SharpCoder

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2 Comments

AFract Over a year ago

What's the purpose of posting exactly the same thing as the accepted answer stackoverflow.com/a/16326071/461444 two years later ?

SharpCoder Over a year ago

@AFract: Check this stackoverflow.com/posts/16326071/revisions the post you mentioned was edited early this year and at that time they updated the original answer added sample for C#

Stefan Steiger · Accepted Answer · 2016-09-14 08:58:54Z

7

To do it in .NET 2.0 (no LINQ), e.g. for SQL-Server ReportingServices without having to write a function for it:

VB.NET

Dim a As String = "", b As String = "b", c As String = "", d As String = "d", e As String = ""
Dim lala As String = String.Join(" / ", String.Join(vbBack, New String() {a, b, c, d, e}).Split(New Char() {ControlChars.Back}, System.StringSplitOptions.RemoveEmptyEntries))

System.Console.WriteLine(lala)

C# (for those landing from google and not searching for VB.NET)

string a = "", b = "b", c = "", d = "d", e = "";
string lala = string.Join(" / ",
    string.Join("\u0008", 
        new string[] { a, b, c, d, e }
    ).Split(new char[] { '\u0008' }, System.StringSplitOptions.RemoveEmptyEntries)
);

System.Console.WriteLine(lala);

This assumes that the character backspace doesn't occur in your strings (should usually be true, because you can't simply enter this character by keyboard).

Also, if you get the values from a database, then it's even simpler, since you can do it in SQL directly:

PostgreSQL & MySQL:

SELECT 
    concat_ws(' / '
        , NULLIF(searchTerm1, '')
        , NULLIF(searchTerm2, '')
        , NULLIF(searchTerm3, '')
        , NULLIF(searchTerm4, '')
    ) AS RPT_SearchTerms;

And even with the glorious MS-SQL-Server it's possible (PS: that's sarcasm):

DECLARE @in_SearchTerm1 nvarchar(100) 
DECLARE @in_SearchTerm2 nvarchar(100) 
DECLARE @in_SearchTerm3 nvarchar(100) 
DECLARE @in_SearchTerm4 nvarchar(100) 

SET @in_SearchTerm1 = N'a'
SET @in_SearchTerm2 = N''
SET @in_SearchTerm3 = N'c'
SET @in_SearchTerm4 = N''

SELECT 
    COALESCE
    (
        STUFF
        (
            (
                SELECT ' / ' + RPT_SearchTerm AS [text()]
                FROM 
                (
                                  SELECT NULLIF(@in_SearchTerm1, N'') AS RPT_SearchTerm, 1 AS RPT_Sort 
                        UNION ALL SELECT NULLIF(@in_SearchTerm2, N'') AS RPT_SearchTerm, 2 AS RPT_Sort  
                        UNION ALL SELECT NULLIF(@in_SearchTerm3, N'') AS RPT_SearchTerm, 3 AS RPT_Sort 
                        UNION ALL SELECT NULLIF(@in_SearchTerm4, N'') AS RPT_SearchTerm, 4 AS RPT_Sort 
                ) AS tempT 
                WHERE RPT_SearchTerm IS NOT NULL 
                ORDER BY RPT_Sort 
                FOR XML PATH(N''), TYPE 
            ).value('.', 'nvarchar(MAX)') 
            ,1
            ,3
            ,N''
        )
        ,N''
    ) AS RPT_SearchTerms

edited Sep 14, 2016 at 8:58

answered Sep 14, 2016 at 8:45

Stefan Steiger

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3 Comments

Doug Over a year ago

SQL Server now has concat_ws() as of SQL Server 2017 (14.x)

Prolog Over a year ago

OP never even mentioned any dabase in his question. This very well may be an anwser, but not to the question posted.

Stefan Steiger Over a year ago

@Doug: i posted in 2016, sql server 2017 wasn't out back then. So yes, now you can use the concat_ws just like in pl/pgsql.

Ryan Naccarato · Accepted Answer · 2022-12-29 17:34:44Z

5

Another option would be to use LINQ's handy null filter:

String.Join(",", myArray.OfType<string>())

edited Dec 29, 2022 at 17:34

answered Dec 12, 2022 at 17:55

Ryan Naccarato

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Comments

user8613096 · Accepted Answer · 2018-08-14 12:24:40Z

0

Try the following:

var finalString = String.Join(",", ExampleArrayOfObjects.Where(x => !String.IsNullOrEmpty(x.TestParameter)).Select(x => x.TestParameter));

answered Aug 14, 2018 at 12:24

user8613096

1 Comment

Inder Over a year ago

kindly consider adding more information in your answer

Aida · Accepted Answer · 2019-02-20 15:41:15Z

-2

This works fine for VB.NET

Join(*yourArray*.Where(Function(s) Not String.IsNullOrEmpty(s)).ToArray(), *yourDelimiter*)

edited Feb 20, 2019 at 15:41

Aida

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answered Feb 20, 2019 at 13:59

user10642724

1

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