StringBuilder class

Hi, this may seem like a trivial question but I want to get a full understanding of when to use this.
I am writing C sharp classes that contain methods which build up a big stream of HTML before passing it back as a String return value, which will then get put into an HTML page via a server control.
At the moment, the code is similar to
String htmlstring =
"

" +
"" +
"" +
"" +
"" +
"" +
"" +
etc etc...
So I have massive big concatenation blocks, then maybe something like
while( reader.Read() )
{
InboxMessage message = InboxMessage.GetMessage( reader.GetInt64( "MessageId" ) );
htmlstring += " : "altmessagerow" ) + " onMouseOver='javascript:RollOverRow(this);' onMouseOut='javascript:RollOutRow(this," + ( currentmessage % 2 ) + ");'>" +
"

" +

Which loops through, concatenating each time. So I have both in-line concatenations being used heavily, and also cross-line using +=.
I want to know the best way to do this, should I leave it as is or will I benefit from using the Stringbuilder class. I am not sure if the String concat overhead just occurs with the += concats, or with all the in-line ones too. ie Does String s = "test" + "hello" + "now"; Create five objects in memory? One for test, one for hello, one for now, and then two for the two concats?
It seems a little heavyweight to use
StringBuilder htmlstring = new StringBuilder("",5000);
htmlstring.Append("");
htmlstring.Append( "");
htmlstring.Append("

");
htmlstring.Append("

");
htmlstring.Append("");
htmlstring.Append("");
htmlstring.Append("");

I'd appreciate anyones advice on this

3 Replies

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Mahesh Chand16y ago
I agree with Sam.
Sam Hobbs16y ago
Another possibility would be to use string.Format.

Something I would do is to create a function to generate each element or set of elements or whatever is appropriate for the requirements.

Actually what I probably would do is to use the DOM to generate the HTML.
Mahesh Chand16y ago
Yes this is correct. Every time you apply any operation on strings in .NET, they create a new allocation in memory. For example,

string str = "mahesh";
str += "chand";

This actually not recycling str object. It would have two memory allocations.

Use StringBuilder and append strings to StringBuilder(). It will create one memory allocation for StringBuilder only.

" + _user.UserName + "