What is capacity and length for StringBuilder ?

Answer:

By specifying capacity you can indicate number of characters the instance object of stringbuilder can hold while the length is the character count of the string the stringbuilder holds.
Specifying lesser capacity and longer string will make capacity to get expanded to accommodate the supplied string. But specifying higher capacity and lesser length will shorten the string content.
Unless specified, the default capacity of the stringbuilder is 16.

    Dim sb As New StringBuilder("Hi", 5) ' initial capacity is set to 5

        Response.Write(sb.Capacity) ' will print 5

        Response.Write(sb.Length) ' will print 2

        sb.Append(" testing")

        Response.Write(sb.Capacity) ' will print 10

        Response.Write(sb.Length) ' will print 10

        sb.Length = 5

        Response.Write(sb) ' will print hi te