GetCharCount Method (Byte*, Int32)

Encoding.GetCharCount Method (Byte*, Int32)


When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer.

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

public virtual unsafe int GetCharCount(
	byte* bytes,
	int count


Type: System.Byte*

A pointer to the first byte to decode.

Type: System.Int32

The number of bytes to decode.

Return Value

Type: System.Int32

The number of characters produced by decoding the specified sequence of bytes.

Exception Condition

bytes is null.


count is less than zero.


A fallback occurred (see Character Encoding in the .NET Framework for complete explanation)


DecoderFallback is set to DecoderExceptionFallback.

To calculate the exact array size that GetChars requires to store the resulting characters, you should use the GetCharCount method. To calculate the maximum array size, use the GetMaxCharCount method. The GetCharCount method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

The GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars method performs the actual decoding. The GetChars method expects discrete conversions, in contrast to the Decoder.GetChars method, which handles multiple passes on a single input stream.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

  • Your app might need to decode multiple input bytes from a code page and process the bytes using multiple calls. In this case, you probably need to maintain state between calls.

  • If your app handles string outputs, it is recommended to use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

  • The byte version of GetChars(Byte*, Int32, Char*, Int32) allows some fast techniques, particularly with multiple calls to large buffers. Bear in mind, however, that this method version is sometimes unsafe, since pointers are required.

  • If your app must convert a large amount of data, it should reuse the output buffer. In this case, the GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

  • Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.


Requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
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