Question

I’m searching the best way to create a string separated with another in a loop. I mean, for example, SQL reader:

StringBuilder sb = new StringBuilder(); while(reader.Read()) {   sb.Append(reader[0]);   sb.Append('<br />'); } string result = sb.ToString(); result = result.Remove(result.LastIndexOf('<br />')); // <- 

or creating SQL query string;

StringBuilder sb = new StringBuilder(); foreach(string v in values) {   sb.Append(v);   sb.Append(','); } string query = sb.ToString() query = query.Remove(query.LastIndexOf(',')); // <- query = String.Concat('INSERT INTO [foo] ([bar]) VALUES(', query, ')'); 

This is the best I have found:

List<string> list = new List<string>; while(reader.Read()) {   list.Add(reader[0]); } string result = String.Join('<br />', list.ToArray()); 

Edit: I know about StringBuilder, I didn’t used it here just for some clarity. My general idea do not use Remove / LastIndexOf !

Answer 1

I am not a fan of StringBuilder unless you really know that you need to worry about performance. It produces ugly code. I would write it this way…

private IEnumerable<string> ReadAllStrings(DataReader reader) {     while(reader.Read())         yield return reader[0]; }   String.Join('<br />', ReadAllStrings(reader).ToArray()); 

If I were doing it a lot, I might consider an extension method:

public static class Extensions {     public static string JoinWith(this IEnumerable<string> strings, string separator)     {         return String.Join(separator, strings.ToArray());     } } 

Then, my code would look like this:

ReadAllStrings(reader).JoinWith('<br />');