Loading data to string variable

[Rostrox]

I am trying to load data to an string variable in the next way: . . . string s = ""; string text = ""; do { If ( text have some conditions) s = s + text + "\n"; text = reader.ReadLine( ); } while (text != null); . . Then I need to show string "s" to user using a multiline textbox created with Web Forms. The problem is that the previous loop lasts many, many minutes. It tries to load 2MB but in a slow manner, I imagine that the memory allocation is the problem. I need textbox for copy/paste purposes. Is there anyway to enhance the speed of s = s + text + "\n"; ??? Best regards.

[Corinna John]

System.Text.StringBuilder is a little faster: StringBuilder s = new StringBuilder(); string text = ""; do { If ( text have some conditions) s.AppendFormat("{1}\n", text); text = reader.ReadLine( ); } while (text != null);

[Jeff Varszegi]

Corinna, Wouldn't this be even a little faster?

StringBuilder s = new StringBuilder();
string text; // No need to assign the variable to a string that's then thrown away
while ((text = reader.readLine()) != null) {
if ( <condition> )
s.Append(text).Append('\n');
}

Regards, Jeff Varszegi [edit] Forgot to include the condition! I'm gonna test the impact of AppendFormat() versus the extra method call. JKV [/edit]

[Jeff Varszegi]

I was interested enough to run a performance test because I never used AppendFormat before, and I know that StringBuilder is highly optimized. I ran this code in Debug mode in VS .NET 2003 on my laptop:

StringBuilder sb;
string text = "abc";
int x, y;
long startTime, endTime;

startTime = DateTime.Now.Ticks;
for(y = 0; y < 5000; y++) {
sb = new StringBuilder(10000);
for (x = 0; x < 250; x++) {
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
sb.Append(text).Append('\n');
}
}
endTime = DateTime.Now.Ticks;
Console.WriteLine(((endTime - startTime) / 10000) + " ms using Append()");

startTime = DateTime.Now.Ticks;
for(y = 0; y < 5000; y++) {
sb = new StringBuilder(10000);
for (x = 0; x < 250; x++) {
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
sb.AppendFormat("{0}\n", text);
}
}
endTime = DateTime.Now.Ticks;
Console.WriteLine(((endTime - startTime) / 10000) + " ms using AppendFormat()");

It printed these results: 1682 ms using Append() 7801 ms using AppendFormat() Interestingly enough, creating a separate variable to hold the format string and using that in calls to AppendFormat increased the run time of the second section a little. I still know next to nothing about the IL, but I'm sure there's some good explanation for this. Regards, Jeff Varszegi