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

Updated: January 2011

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

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

public StringBuilder Append(
	char[] value,
	int startIndex,
	int charCount


Type: System.Char[]

A character array.

Type: System.Int32

The zero-based 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 null, 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 null 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.

char[] chars = { 'a', 'b', 'c', 'd', 'e'};
System.Text.StringBuilder sb = new System.Text.StringBuilder();
int startPosition = Array.IndexOf(chars, 'a');
int endPosition = Array.IndexOf(chars, 'c');
if (startPosition >= 0 && endPosition >= 0) {
   sb.Append("The array from positions ").Append(startPosition).
             Append(" to ").Append(endPosition).Append(" contains ").
             Append(chars, startPosition, endPosition + 1).Append(".");
// The example displays the following output: 
//       The array from positions 0 to 2 contains abc.

The capacity of this instance is adjusted as needed.

The following example uses the Append(Char[], Int32, Int32) method to append a set of characters to a string.

char[] characters = {'/', '<', '<', ' ', '>', '>', '\\'};
const int beginPosition = 0;
const int endPosition = 3; 

string title = "The Hound of the Baskervilles";

StringBuilder sb = new StringBuilder();
sb.Append(characters, beginPosition, 4);
sb.Append(characters, endPosition, 4);
// The example displays the following output: 
//      /<< The Hound of the Baskervilles >>\      

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0




January 2011

Expanded the Remarks section.

Customer feedback.

August 2008

Replaced example.

Customer feedback.

Community Additions

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