Stringbuilder is an internal class provided by C# that helps us to improve string manipulation functions. To explain the idea, we will be executing a for loop from 0 to 100 and will be concatenating the resultant output in each loop with the letter a. Internally, a string builder uses a buffer to modify the string value instead of allocating memory on every string manipulation. The following code example shows how we can use string builder for string manipulation operations:

StringBuilder sb = new StringBuilder(string.Empty);
for (int z = 0; z < 100; z++)
{
     sb.Append("a"); 
}

In the preceding code, we are declaring a StringBuilder object, sb, and are appending its value with a in the loop. Internally, instead of allocating memory on every concatenation, StringBuilder will use an internal buffer to manage these operations.