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StringBuilder.Append Method (Char(), Int32, Int32)

Appends the string representation of a specified subarray of Unicode characters to this instance.

Namespace:  System.Text
Assembly:  mscorlib (in mscorlib.dll)

Public Function Append ( _
	value As Char(), _
	startIndex As Integer, _
	charCount As Integer _
) As StringBuilder


Type: System.Char()
A character array.
Type: System.Int32
The starting position in value.
Type: System.Int32
The number of characters to append.

Return Value

Type: System.Text.StringBuilder
A reference to this instance after the append operation has completed.


value is Nothing, and startIndex and charCount are not zero.


charCount is less than zero.


startIndex is less than zero.


startIndex + charCount is greater than the length of value.


Enlarging the value of this instance would exceed MaxCapacity.

This method appends the specified range of characters in value to the current instance. If value is Nothing and startIndex and count are both zero, no changes are made.

The Append method modifies the existing instance of this class; it does not return a new class instance. Because of this, you can call a method or property on the existing reference and you do not have to assign the return value to a StringBuilder object, as the following example illustrates.

Dim chars() As Char = { "a"c, "b"c, "c"c, "d"c, "e"c}
Dim sb As New System.Text.StringBuilder()
Dim startPosition As Integer = Array.IndexOf(chars, "a"c)
Dim endPosition As Integer = Array.IndexOf(chars, "c"c)
If startPosition >= 0 AndAlso endPosition >= 0 Then
   sb.Append("The array from positions ").Append(startPosition).
             Append(" to ").Append(endPosition).Append(" contains ").
             Append(chars, startPosition, endPosition + 1).Append(".")
End If             
' The example displays the following output:
'       The array from positions 0 to 2 contains abc.

The capacity of this instance is adjusted as needed.

Notes to Callers

In the .NET Framework 4, when you instantiate the StringBuilder object by calling the StringBuilder constructor, both the length and the capacity of the StringBuilder instance can grow beyond the value of its MaxCapacity property. This can occur particularly when you call the Append and AppendFormat methods to append small strings.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.