The StringBuilder class provides the developer with a set of methods that allows manipulation of a mutable string of characters, it can be used when you want to modify a string without creating a new object, thus eliminating the overhead or bottleneck issue of the normal String concatenation.
Using the StringBuilder class can boost performance when concatenating many strings together in a loop.
To use StringBuilder class, you need to make sure you are using the namespace
The following is a list of a few operations that can be performed to manipulate a string using the StringBuilder Class in .NET
Append: Appends information to the end of the current StringBuilder.
AppendLine: Appends information as well as the default line terminator to the end of the current StringBuilder.
AppendFormat: Replaces a format specifier passed in a string with formatted text.
Insert: Inserts a string or object into the specified index of the current StringBuilder.
Remove: Removes a specified number of characters from the current StringBuilder.
Replace: Replaces a specified character at a specified index.
For the complete list of available methods in StringBuilder class, please refer to Microsoft's documentation here