UTF8Encoding.GetMaxByteCount(Int32) Method

Reference

Definition

Namespace:: System.Text

Assemblies:: mscorlib.dll, System.Text.Encoding.Extensions.dll

Assemblies:: netstandard.dll, System.Text.Encoding.Extensions.dll

Assembly:: System.Text.Encoding.Extensions.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: UTF8Encoding.cs

Source:: UTF8Encoding.cs

Source:: UTF8Encoding.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Calculates the maximum number of bytes produced by encoding the specified number of characters.

public:
 override int GetMaxByteCount(int charCount);

public override int GetMaxByteCount(int charCount);

override this.GetMaxByteCount : int -> int

Public Overrides Function GetMaxByteCount (charCount As Integer) As Integer

Parameters

charCount: Int32

The number of characters to encode.

Returns

Int32

The maximum number of bytes produced by encoding the specified number of characters.

Exceptions

ArgumentOutOfRangeException

charCount is less than zero.

-or-

The resulting number of bytes is greater than the maximum number that can be returned as an integer.

EncoderFallbackException

A fallback occurred (for more information, see Character Encoding in .NET)

-and-

EncoderFallback is set to EncoderExceptionFallback.

Examples

The following example uses the GetMaxByteCount method to return the maximum number of bytes required to encode a specified number of characters.

using namespace System;
using namespace System::Text;
int main()
{
   UTF8Encoding^ utf8 = gcnew UTF8Encoding;
   int charCount = 2;
   int maxByteCount = utf8->GetMaxByteCount( charCount );
   Console::WriteLine( "Maximum of {0} bytes needed to encode {1} characters.", maxByteCount, charCount );
}

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        UTF8Encoding utf8 = new UTF8Encoding();
        int charCount = 2;
        int maxByteCount = utf8.GetMaxByteCount(charCount);
        Console.WriteLine(
            "Maximum of {0} bytes needed to encode {1} characters.",
            maxByteCount,
            charCount
        );
    }
}

Imports System.Text

Class UTF8EncodingExample
    
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim charCount As Integer = 2
        Dim maxByteCount As Integer = utf8.GetMaxByteCount(charCount)
        Console.WriteLine( _
            "Maximum of {0} bytes needed to encode {1} characters.", _
            maxByteCount, _
            charCount _
        )
    End Sub
End Class

Remarks

To calculate the exact array size required by GetBytes to store the resulting bytes, you call the GetByteCount method. To calculate the maximum array size, you call the GetMaxByteCount method. The GetByteCount method generally allocates less memory, while the GetMaxByteCount method generally executes faster.

GetMaxByteCount is a worst-case number, including the worst case for the currently selected EncoderFallback. If a fallback is chosen with a potentially large string, GetMaxByteCount can return large values.

In most cases, this method returns reasonable numbers for small strings. For large strings, you might have to choose between using very large buffers and catching errors in the rare case that a more reasonable buffer is exceeded. You might also want to consider a different approach using GetByteCount or Encoder.Convert. For example, text in English and many other languages often needs only one UTF-8 byte to represent a character, but the number returned by GetMaxByteCount has to allow for the possibility that the string to be converted will consist entirely of characters that each require four bytes.

GetMaxByteCount has no relation to GetChars. If your application needs a similar function to use with GetChars, it should use GetMaxCharCount.

Бележка

GetMaxByteCount(N) is not necessarily the same value as N* GetMaxByteCount(1).

Applies to

Продукт	Версии
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1
UWP	10.0

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