string builder and string

[sivak]

can anypone explain me string builder and string with good example ?

[sknake]

From the help file for string builder under "Performance Considerations":

The performance of a concatenation operation for a String or StringBuilder object depends on how often a memory allocation occurs. A String concatenation operation always allocates memory, whereas a StringBuilder concatenation operation only allocates memory if the StringBuilder object buffer is too small to accommodate the new data. Consequently, the String class is preferable for a concatenation operation if a fixed number of String objects are concatenated. In that case, the individual concatenation operations might even be combined into a single operation by the compiler. A StringBuilder object is preferable for a concatenation operation if an arbitrary number of strings are concatenated; for example, if a loop concatenates a random number of strings of user input.

Execution Time: 20234.375

private void simpleButton1_Click(object sender, EventArgs e)
    {
      string s = new string('x', 6000);
      DateTime dtStart = DateTime.Now;
      string result = string.Empty;
      for (int i1 = 0; i1 < 1900; i1++)
      {
        result += s;
      }
      DateTime dtEnd = DateTime.Now;

      double milliSecTaken = dtEnd.Subtract(dtStart).TotalMilliseconds;
      Console.WriteLine(milliSecTaken);
    }

Execution Time: 62.5

private void simpleButton1_Click(object sender, EventArgs e)
    {
      string s = new string('x', 6000);
      DateTime dtStart = DateTime.Now;
      string result = string.Empty;
      StringBuilder sb = new StringBuilder();
      for (int i1 = 0; i1 < 1900; i1++)
      {
        sb.AppendLine(s);
      }
      result = sb.ToString();
      DateTime dtEnd = DateTime.Now;

      double milliSecTaken = dtEnd.Subtract(dtStart).TotalMilliseconds;
      Console.WriteLine(milliSecTaken); 
    }

Having to reallocate a new string which is increasing in size every iteration of the loop kills performance in the first code snippet. The second code snippet uses a string builder and does not suffer from the same performance degredation as the first snippet.

[kvprajapati]

Thanks sknake, Informative thread.

I would like to add few things:

StringBuilder represents a mutable string of characters - it can be modified once it has been created by appending, removing, replacing, or inserting characters.

String objects are immutable. Its value cannot be modified once it has been created.

[sivak]

in the above example u were used both string an dstring builder as well..which on is best..as my knowlegde stringbuilder is good..explain me with good understanding example with brief detail plz

[sknake]

StringBuilder is better as a general statement. In some minor cases it will taken longer than appending to a string but these should largely be ignored. I gave you the time taken to require each operation and it took significantly longer without using the StringBuilder.

[serkan sendur]

have a look at the attached.