RE: Clean way to do string.join

Optimizing Criag's approach (and putting it in a method for reuse):

using System.Text;

public static string JoinNonempty( string separator, string [] value )
{
  StringBuilder sb = new StringBuilder();
  int i = 0;
  for ( ; i < value.Length && value[i] == string.Empty; ++i ) ;

  if ( i < value.Length )
  {
    sb.Append( value[ i++ ] );
    for ( ; i < value.Length; ++i )
      if ( value[i] != string.Empty  )
        sb.AppendFormat ( "{0}{1}", separator, value[i] );
  }

  return sb.ToString();
}

Sample usage:

string [] value = { "", "B", "", "D", "" };
Console.WriteLine( JoinNonempty( " AND ", value ));

This produces the output "B AND D".


But that's a lot of logic, i.e., ample opportunity to get something wrong. A
simpler approach would be to filter the string array first, then use the
tested-and-tried string.Join method:

Using System.Collections;

public static string[] CopyNonempty( string [] value )
{
  ArrayList list = new ArrayList();
  foreach ( string s in value )
    if ( s != string.Empty ) list.Add( s );

  return list.ToArray( typeof( string ) ) as string [] ;
}

Sample usage:

string [] value = { "", "B", "", "D", "" };
Console.WriteLine( string.Join( " AND ", CopyNonempty( value ) ) );


All other things (like performance) being equal I would prefer the second
approach. It is easier code to review and maintain, and there is more
opportunity to reuse the CopyNonempty method in other settings.

Cheers,
Stuart

Stuart Celarier | Fern Creek | www.ferncrk.com


-----Original Message-----
From: Craig Wagner [mailto:craig.wagner@xxxxxxxxx] 
Sent: Wednesday, January 26, 2005 8:06 AM
To: padnug@xxxxxxxxxxxxxxx
Subject: Re: [padnug] Clean way to do string.join


Try this...

        string [] stuff = { "X", "", "Z", "" };
        StringBuilder result = new StringBuilder( 50 );
        
        for( int i = 0; i < stuff.Length; i++ )
        {
            result.Append( ( result.Length > 0 && stuff[i].Length > 0
? " AND " : "" ) + stuff[i] );
        }

The result of the above was: X AND Z

To answer your question, I think String.Join is behaving exactly as I
would expect. It might be nice if it had an overload that allowed you
to tell it to ignore zero-length strings, but I wouldn't expect the
default behavior to do anything other than what it is doing.

On Tue, 25 Jan 2005 18:07:54 -0800, Zhong, Clark Y
<clark.y.zhong@xxxxxxxxx> wrote:
> 
> Hi all:
> 
>             I like to use a lot string functions since formulating an
> expression can be a pain.   I tried to use string.join to make a simple
> AND clause, "X AND Y AND Z", any of them can be empty, i.e., if X is
> empty, it becomes "Y AND Z".   However I noticed string.join is not that
> smart, it does not treat empty string or null string differently, and
> output " AND Y AND Z".
> 
>             I hate to do an elaborate if else since I need to do
> multiple branches for different combinations.  Any efficient way to
> address string.join's short coming?  Shouldn't it no do a join if string
> element is empty?


 
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