dotnet-api-docs/xml/System.Text/Decoder.xml at main · dotnet/dotnet-api-docs

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<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

</TypeForwardingChain>

<Base>

<BaseTypeName>System.Object</BaseTypeName>

</Base>

<AttributeName Language="C#">[System.Serializable]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(true)]</AttributeName>

</Attribute>

</Attributes>

<Docs>

<summary>Converts a sequence of encoded bytes into a set of characters.</summary>

<format type="text/markdown"><![CDATA[

To obtain an instance of an implementation of the <xref:System.Text.Decoder> class, call the <xref:System.Text.Encoding.GetDecoder%2A> method of an <xref:System.Text.Encoding> implementation.

The <xref:System.Text.Decoder.GetCharCount%2A> method determines how many characters result in decoding a sequence of bytes, and the <xref:System.Text.Decoder.GetChars%2A> method performs the actual decoding. There are several versions of both of these methods available in the <xref:System.Text.Decoder> class. For more information, see <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType>. A <xref:System.Text.Decoder> object maintains state information between successive calls to `GetChars` or <xref:System.Text.Decoder.Convert%2A> methods so it can correctly decode byte sequences that span blocks. The <xref:System.Text.Decoder> also preserves trailing bytes at the end of data blocks and uses the trailing bytes in the next decoding operation. Therefore, <xref:System.Text.Encoding.GetDecoder%2A> and <xref:System.Text.Encoding.GetEncoder%2A> are useful for network transmission and file operations because those operations often deal with blocks of data instead of a complete data stream.

> [!NOTE]

> When the application is done with a stream of data, it should make sure that the state information is flushed by setting the `flush` parameter to `true` in the appropriate method call. If an exception occurs or if the application switches streams, it should call <xref:System.Text.Decoder.Reset%2A> to clear the internal state of the `Decoder` object.

]]></format>

</remarks>

<format type="text/markdown"><![CDATA[

The following example demonstrates the use of a <xref:System.Text.Decoder> to convert two different byte arrays into a character array. One of the character's bytes spans the arrays. This is similar to what a <xref:System.IO.StreamReader> object does internally when reading a stream.

:::code language="csharp" source="~/snippets/csharp/System.Text/Decoder/Overview/source.cs" id="Snippet1":::

:::code language="vb" source="~/snippets/visualbasic/System.Text/Decoder/Overview/source.vb" id="Snippet1":::

]]></format>

</example>

<para>When your application inherits from this class, it must override all the members.</para>

</block>

<related type="Article" href="/dotnet/standard/base-types/character-encoding">Understanding Encodings</related>

</Docs>

<MemberType>Constructor</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<Docs>

<summary>Initializes a new instance of the <see cref="T:System.Text.Decoder" /> class.</summary>

<format type="text/markdown"><![CDATA[

## Remarks

To obtain an instance of an implementation of this class, the application should use the <xref:System.Text.Encoding.GetDecoder%2A> method of a <xref:System.Text.Encoding> implementation.

## Examples

The following example demonstrates two techniques for initializing a new <xref:System.Text.Decoder> instance.

:::code language="csharp" source="~/snippets/csharp/System.Text/Decoder/.ctor/ctor.cs" id="Snippet1":::

:::code language="vb" source="~/snippets/visualbasic/System.Text/Decoder/.ctor/ctor.vb" id="Snippet1":::

]]></format>

</remarks>

</Docs>

</Member>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<Docs>

<summary>Converts an encoded byte sequence to a string or array of characters.</summary>

<format type="text/markdown"><![CDATA[

## Remarks

Remember that the <xref:System.Text.Decoder> object saves state between calls to <xref:System.Text.Decoder.Convert%2A>.

When the application is done with a stream of data, it should set the `flush` parameter to `true` to make sure that the state information is flushed. With this setting, the decoder ignores invalid bytes at the end of the data block and clears the internal buffer.

Any remaining processed data that is part of a logical unit, such as the high surrogate of a surrogate pair, is converted according to the current fallback settings.

The `Convert` method is designed to be used in a loop to decode an arbitrary amount of input, such as data read from a file or stream.

It stores the output of the decoding operation in a fixed-size buffer.

<xref:System.Text.Decoder.GetChars%2A> will throw an exception if the output buffer isn't large enough, but <xref:System.Text.Decoder.Convert%2A> will fill as much space as possible and return the bytes read and chars written, provided the output array allows for at least two characters.

Also see <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> for more comments.

]]></format>

</remarks>

</Docs>

</MemberGroup>

<MemberSignature Language="C#" Value="public virtual void Convert (ReadOnlySpan<byte> bytes, Span<char> chars, bool flush, out int bytesUsed, out int charsUsed, out bool completed);" />

<MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance void Convert(valuetype System.ReadOnlySpan`1<unsigned int8> bytes, valuetype System.Span`1<char> chars, bool flush, [out] int32& bytesUsed, [out] int32& charsUsed, [out] bool& completed) cil managed" />

<MemberSignature Language="F#" Value="abstract member Convert : ReadOnlySpan<byte> * Span<char> * bool * int * int * bool -> unit
override this.Convert : ReadOnlySpan<byte> * Span<char> * bool * int * int * bool -> unit" Usage="decoder.Convert (bytes, chars, flush, bytesUsed, charsUsed, completed)" />

<MemberSignature Language="C++ CLI" Value="public:
 virtual void Convert(ReadOnlySpan<System::Byte> bytes, Span<char> chars, bool flush, [Runtime::InteropServices::Out] int % bytesUsed, [Runtime::InteropServices::Out] int % charsUsed, [Runtime::InteropServices::Out] bool % completed);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<ReturnType>System.Void</ReturnType>

</ReturnValue>

<Parameter Name="bytes" Type="System.ReadOnlySpan<System.Byte>" Index="0" FrameworkAlternate="netcore-2.1;netcore-2.2;netcore-3.0;netstandard-2.1;netcore-3.1;net-5.0;net-6.0;net-7.0;net-8.0;net-9.0;net-10.0;net-11.0" />

<Parameter Name="chars" Type="System.Span<System.Char>" Index="1" FrameworkAlternate="netcore-2.1;netcore-2.2;netcore-3.0;netstandard-2.1;netcore-3.1;net-5.0;net-6.0;net-7.0;net-8.0;net-9.0;net-10.0;net-11.0" />

</Parameters>

<Docs>

<param name="bytes">A read-only bytes span containing the sequence to convert.</param>

<param name="chars">The span to store the converted characters.</param>

<see langword="true" /> to indicate no further data is to be converted; otherwise, <see langword="false" />.</param>

<param name="bytesUsed">When this method returns, contains the number of bytes that were produced by the conversion. This parameter is passed uninitialized.</param>

<param name="charsUsed">When this method returns, contains the number of characters from <paramref name="chars" /> that were used in the conversion. This parameter is passed uninitialized.</param>

<param name="completed">When this method returns, contains <see langword="true" /> if all the specified characters were converted; otherwise, <see langword="false" />. This parameter is passed uninitialized.</param>

<summary>Converts a span of encoded bytes to UTF-16 encoded characters and stores the result in another span buffer.</summary>

<format type="text/markdown"><![CDATA[

## Remarks

The `completed` output parameter indicates whether all the data in the input bytes span was converted and stored in the chars span. This parameter is set to `false` if the number of bytes contained in the input bytes span cannot be converted without exceeding the number of characters in the chars span. In that situation, the application should use the contents of the output buffer or provide a new output buffer, increment the `bytes` parameter by the number of bytes specified by the `bytesUsed` parameter, then call the `Convert` method again to process the remaining input.

The `completed` parameter can also be set to `false`, even though the `bytesUsed` parameter and bytes span length are equal. This situation occurs if there is still data in the <xref:System.Text.Decoder> object that has not been stored in the `bytes` span.

]]></format>

</remarks>

</Docs>

</Member>

<MemberSignature Language="F#" Value="abstract member Convert : nativeptr<byte> * int * nativeptr<char> * int * bool * int * int * bool -> unit
override this.Convert : nativeptr<byte> * int * nativeptr<char> * int * bool * int * int * bool -> unit" Usage="decoder.Convert (bytes, byteCount, chars, charCount, flush, bytesUsed, charsUsed, completed)" />

<MemberType>Method</MemberType>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.CLSCompliant(false)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Security.SecurityCritical]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Void</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">The address of a buffer that contains the byte sequences to convert.</param>

<param name="byteCount">The number of bytes in <paramref name="bytes" /> to convert.</param>

<param name="chars">The address of a buffer to store the converted characters.</param>

<param name="charCount">The maximum number of characters in <paramref name="chars" /> to use in the conversion.</param>

<see langword="true" /> to indicate no further data is to be converted; otherwise, <see langword="false" />.</param>

<param name="bytesUsed">When this method returns, contains the number of bytes that were produced by the conversion. This parameter is passed uninitialized.</param>

<param name="charsUsed">When this method returns, contains the number of characters from <paramref name="chars" /> that were used in the conversion. This parameter is passed uninitialized.</param>

<param name="completed">When this method returns, contains <see langword="true" /> if all the characters specified by <paramref name="byteCount" /> were converted; otherwise, <see langword="false" />. This parameter is passed uninitialized.</param>

<summary>Converts a buffer of encoded bytes to UTF-16 encoded characters and stores the result in another buffer.</summary>

<format type="text/markdown"><![CDATA[

## Remarks

The `completed` output parameter indicates whether all the data in the input buffer was converted and stored in the output buffer. This parameter is set to `false` if the number of bytes specified by the `byteCount` parameter cannot be converted without exceeding the number of characters specified by the `charCount` parameter. In that situation, the application should use the contents of the output buffer or provide a new output buffer, increment the `bytes` parameter by the number of bytes specified by the `bytesUsed` parameter, then call the `Convert` method again to process the remaining input.

The `completed` parameter can also be set to `false`, even though the `bytesUsed` and `byteCount` parameters are equal. This situation occurs if there is still data in the <xref:System.Text.Decoder> object that has not been stored in the `bytes` buffer.

]]></format>

</remarks>

<exception cref="T:System.ArgumentException">The output buffer is too small to contain any of the converted input. The output buffer should be at least 2 chars in size to accomodate at least one surrogate character pair.</exception>

<exception cref="T:System.Text.DecoderFallbackException">A fallback occurred (for more information, see <see href="https://learn.microsoft.com/dotnet/standard/base-types/character-encoding">Character Encoding in .NET</see>)

-and-

</Docs>

</Member>

<MemberSignature Language="F#" Value="abstract member Convert : byte[] * int * int * char[] * int * int * bool * int * int * bool -> unit
override this.Convert : byte[] * int * int * char[] * int * int * bool * int * int * bool -> unit" Usage="decoder.Convert (bytes, byteIndex, byteCount, chars, charIndex, charCount, flush, bytesUsed, charsUsed, completed)" />

<MemberSignature Language="C++ CLI" Value="public:
 virtual void Convert(cli::array <System::Byte> ^ bytes, int byteIndex, int byteCount, cli::array <char> ^ chars, int charIndex, int charCount, bool flush, [Runtime::InteropServices::Out] int % bytesUsed, [Runtime::InteropServices::Out] int % charsUsed, [Runtime::InteropServices::Out] bool % completed);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Void</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">A byte array to convert.</param>

<param name="byteIndex">The first element of <paramref name="bytes" /> to convert.</param>

<param name="byteCount">The number of elements of <paramref name="bytes" /> to convert.</param>

<param name="chars">An array to store the converted characters.</param>

<param name="charIndex">The first element of <paramref name="chars" /> in which data is stored.</param>

<param name="charCount">The maximum number of elements of <paramref name="chars" /> to use in the conversion.</param>

<see langword="true" /> to indicate that no further data is to be converted; otherwise, <see langword="false" />.</param>

<param name="bytesUsed">When this method returns, contains the number of bytes that were used in the conversion. This parameter is passed uninitialized.</param>

<param name="charsUsed">When this method returns, contains the number of characters from <paramref name="chars" /> that were produced by the conversion. This parameter is passed uninitialized.</param>

<summary>Converts an array of encoded bytes to UTF-16 encoded characters and stores the result in a character array.</summary>

<format type="text/markdown"><![CDATA[

## Remarks

## Examples

The following example uses the <xref:System.Text.Encoder.Convert%2A> method to convert a file of UTF-16 characters to UTF-8. It then uses the <xref:System.Text.Decoder.Convert%2A> method to convert the UTF-8 characters back to UTF-16 characters.

:::code language="csharp" source="~/snippets/csharp/System.Text/Decoder/Convert/edCvt.cs" id="Snippet1":::

:::code language="vb" source="~/snippets/visualbasic/System.Text/Decoder/Convert/edCvt.vb" id="Snippet1":::

]]></format>

</remarks>

<paramref name="charIndex" />, <paramref name="charCount" />, <paramref name="byteIndex" />, or <paramref name="byteCount" /> is less than zero.

-or-

The length of <paramref name="chars" /> - <paramref name="charIndex" /> is less than <paramref name="charCount" />.

-or-

The length of <paramref name="bytes" /> - <paramref name="byteIndex" /> is less than <paramref name="byteCount" />.</exception>

-and-

</Docs>

</Member>

<MemberType>Property</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.Runtime.CompilerServices.Nullable(2)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Text.DecoderFallback</ReturnType>

</ReturnValue>

<Docs>

<summary>Gets or sets a <see cref="T:System.Text.DecoderFallback" /> object for the current <see cref="T:System.Text.Decoder" /> object.</summary>

<value>A <see cref="T:System.Text.DecoderFallback" /> object.</value>

<format type="text/markdown"><![CDATA[

## Remarks

The <xref:System.Text.DecoderFallback> object represents an error handler that is invoked when an encoded byte sequence cannot be converted to a character.

]]></format>

</remarks>

<exception cref="T:System.ArgumentNullException">The value in a set operation is <see langword="null" /> (<see langword="Nothing" />).</exception>

<exception cref="T:System.ArgumentException">A new value cannot be assigned in a set operation because the current <see cref="T:System.Text.DecoderFallbackBuffer" /> object contains data that has not been decoded yet.</exception>

<related type="Article" href="/dotnet/standard/base-types/character-encoding">Understanding Encodings</related>

</Docs>

</Member>

<MemberType>Property</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.Runtime.CompilerServices.Nullable(1)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Text.DecoderFallbackBuffer</ReturnType>

</ReturnValue>

<Docs>

<summary>Gets the <see cref="T:System.Text.DecoderFallbackBuffer" /> object associated with the current <see cref="T:System.Text.Decoder" /> object.</summary>

<value>A <see cref="T:System.Text.DecoderFallbackBuffer" /> object.</value>

<format type="text/markdown"><![CDATA[

## Remarks

The <xref:System.Text.DecoderFallbackBuffer> object represents data used by the <xref:System.Text.DecoderFallback> object. The <xref:System.Text.DecoderFallback> object represents an error handler that is invoked when an encoded byte sequence cannot be converted to a character.

]]></format>

</remarks>

</Docs>

</Member>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<Docs>

<summary>When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes.</summary>

</Docs>

</MemberGroup>

<MemberSignature Language="C#" Value="public virtual int GetCharCount (ReadOnlySpan<byte> bytes, bool flush);" />

<MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance int32 GetCharCount(valuetype System.ReadOnlySpan`1<unsigned int8> bytes, bool flush) cil managed" />

<MemberSignature Language="F#" Value="abstract member GetCharCount : ReadOnlySpan<byte> * bool -> int
override this.GetCharCount : ReadOnlySpan<byte> * bool -> int" Usage="decoder.GetCharCount (bytes, flush)" />

<MemberSignature Language="C++ CLI" Value="public:
 virtual int GetCharCount(ReadOnlySpan<System::Byte> bytes, bool flush);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<ReturnType>System.Int32</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">A byte span to decode.</param>

<see langword="true" /> to simulate clearing the internal state of the encoder after the calculation; otherwise, <see langword="false" />.</param>

<summary>When overridden in a derived class, calculates the number of characters produced by decoding the sequence of bytes in the span. A parameter indicates whether to clear the internal state of the decoder after the calculation.</summary>

<returns>The number of characters produced by decoding the specified sequence of bytes and any bytes in the internal buffer.</returns>

<format type="text/markdown"><![CDATA[

## Remarks

This method does not affect the state of the decoder.

To calculate the exact buffer size that <xref:System.Text.Decoder.GetChars%2A> requires to store the resulting characters, the application should use <xref:System.Text.Decoder.GetCharCount%2A>.

If `GetChars` is called with `flush` set to `false`, the decoder stores trailing bytes at the end of the data block in an internal buffer and uses them in the next decoding operation. The application should call `GetCharCount` on a block of data immediately before calling `GetChars` on the same block, so that any trailing bytes from the previous block are included in the calculation.

]]></format>

</remarks>

</Docs>

</Member>

<MemberSignature Language="F#" Value="abstract member GetCharCount : nativeptr<byte> * int * bool -> int
override this.GetCharCount : nativeptr<byte> * int * bool -> int" Usage="decoder.GetCharCount (bytes, count, flush)" />

<MemberType>Method</MemberType>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.CLSCompliant(false)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

<AttributeName Language="C#">[System.Security.SecurityCritical]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Int32</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">A pointer to the first byte to decode.</param>

<param name="count">The number of bytes to decode.</param>

<see langword="true" /> to simulate clearing the internal state of the encoder after the calculation; otherwise, <see langword="false" />.</param>

<summary>When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer. A parameter indicates whether to clear the internal state of the decoder after the calculation.</summary>

<returns>The number of characters produced by decoding the specified sequence of bytes and any bytes in the internal buffer.</returns>

<format type="text/markdown"><![CDATA[

## Remarks

This method does not affect the state of the decoder.

To calculate the exact array size that <xref:System.Text.Decoder.GetChars%2A> requires to store the resulting characters, the application should use <xref:System.Text.Decoder.GetCharCount%2A>.

]]></format>

</remarks>

<paramref name="bytes" /> is <see langword="null" /> (<see langword="Nothing" /> in Visual Basic .NET).</exception>

-and-

</Docs>

</Member>

<MemberSignature Language="F#" Value="abstract member GetCharCount : byte[] * int * int -> int" Usage="decoder.GetCharCount (bytes, index, count)" />

<MemberSignature Language="C++ CLI" Value="public:
 abstract int GetCharCount(cli::array <System::Byte> ^ bytes, int index, int count);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<ReturnType>System.Int32</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">The byte array containing the sequence of bytes to decode.</param>

<param name="index">The index of the first byte to decode.</param>

<param name="count">The number of bytes to decode.</param>

<summary>When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.</summary>

<returns>The number of characters produced by decoding the specified sequence of bytes and any bytes in the internal buffer.</returns>

<format type="text/markdown"><![CDATA[

## Remarks

This method does not affect the state of the decoder.

To calculate the exact array size that <xref:System.Text.Decoder.GetChars%2A> requires to store the resulting characters, the application should use <xref:System.Text.Decoder.GetCharCount%2A>.

## Examples

The following code example demonstrates how to use the <xref:System.Text.Decoder.GetCharCount%2A> method to calculate the number of characters required to decode the specified range of bytes in the array.

:::code language="csharp" source="~/snippets/csharp/System.Text/Decoder/GetCharCount/getcharcount-byte[]-int32-int32.cs" id="Snippet1":::

:::code language="vb" source="~/snippets/visualbasic/System.Text/Decoder/GetCharCount/getcharcount-byte[]-int32-int32.vb" id="Snippet1":::

]]></format>

</remarks>

<paramref name="index" /> or <paramref name="count" /> is less than zero.

-or-

<paramref name="index" /> and <paramref name="count" /> do not denote a valid range in <paramref name="bytes" />.</exception>

-and-

</Docs>

</Member>

<MemberSignature Language="F#" Value="abstract member GetCharCount : byte[] * int * int * bool -> int
override this.GetCharCount : byte[] * int * int * bool -> int" Usage="decoder.GetCharCount (bytes, index, count, flush)" />

<MemberSignature Language="C++ CLI" Value="public:
 virtual int GetCharCount(cli::array <System::Byte> ^ bytes, int index, int count, bool flush);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(false)]</AttributeName>

</Attribute>

</Attributes>

<ReturnType>System.Int32</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">The byte array containing the sequence of bytes to decode.</param>

<param name="index">The index of the first byte to decode.</param>

<param name="count">The number of bytes to decode.</param>

<see langword="true" /> to simulate clearing the internal state of the encoder after the calculation; otherwise, <see langword="false" />.</param>

<summary>When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array. A parameter indicates whether to clear the internal state of the decoder after the calculation.</summary>

<returns>The number of characters produced by decoding the specified sequence of bytes and any bytes in the internal buffer.</returns>

<format type="text/markdown"><![CDATA[

## Remarks

This method does not affect the state of the decoder.

To calculate the exact array size that <xref:System.Text.Decoder.GetChars%2A> requires to store the resulting characters, the application should use <xref:System.Text.Decoder.GetCharCount%2A>.

]]></format>

</remarks>

<paramref name="index" /> or <paramref name="count" /> is less than zero.

-or-

<paramref name="index" /> and <paramref name="count" /> do not denote a valid range in <paramref name="bytes" />.</exception>

-and-

</Docs>

</Member>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<Docs>

<summary>When overridden in a derived class, decodes a sequence of bytes into a set of characters.</summary>

</Docs>

</MemberGroup>

<MemberSignature Language="C#" Value="public virtual int GetChars (ReadOnlySpan<byte> bytes, Span<char> chars, bool flush);" />

<MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance int32 GetChars(valuetype System.ReadOnlySpan`1<unsigned int8> bytes, valuetype System.Span`1<char> chars, bool flush) cil managed" />

<MemberSignature Language="F#" Value="abstract member GetChars : ReadOnlySpan<byte> * Span<char> * bool -> int
override this.GetChars : ReadOnlySpan<byte> * Span<char> * bool -> int" Usage="decoder.GetChars (bytes, chars, flush)" />

<MemberSignature Language="C++ CLI" Value="public:
 virtual int GetChars(ReadOnlySpan<System::Byte> bytes, Span<char> chars, bool flush);" />

<MemberType>Method</MemberType>

<AssemblyName>System.Runtime</AssemblyName>

</AssemblyInfo>

<AssemblyName>mscorlib</AssemblyName>

</AssemblyInfo>

<AssemblyName>netstandard</AssemblyName>

</AssemblyInfo>

<AssemblyName>System.Text.Encoding</AssemblyName>

</AssemblyInfo>

<ReturnType>System.Int32</ReturnType>

</ReturnValue>

</Parameters>

<Docs>

<param name="bytes">A byte span to decode.</param>

<param name="chars">A span to write the resulting set of characters.</param>

<see langword="true" /> to clear the internal state of the decoder after the conversion; otherwise, <see langword="false" />.</param>

<summary>When overridden in a derived class, decodes a sequence of span bytes and any bytes in the internal buffer into a set of characters that are stored starting at the specified character pointer. A parameter indicates whether to clear the internal state of the decoder after the conversion.</summary>

<returns>The actual number of characters written at the span indicated by the <paramref name="chars" /> parameter.</returns>

<format type="text/markdown"><![CDATA[

## Remarks

Remember that the <xref:System.Text.Decoder> object saves state between calls to <xref:System.Text.Decoder.GetChars%2A>. When the application is done with a stream of data, it should set the `flush` parameter to `true` to make sure that the state information is flushed. With this setting, the decoder ignores invalid bytes at the end of the data block and clears the internal buffer.

To calculate the exact span size that `GetChars` requires to store the resulting characters, the application should use <xref:System.Text.Decoder.GetCharCount%2A>.

If your application is to convert many segments of an input stream, consider using the <xref:System.Text.Decoder.Convert%2A> method. <xref:System.Text.Decoder.GetChars%2A> will throw an exception if the output span isn't large enough, but <xref:System.Text.Decoder.Convert%2A> will fill as much space as possible and return the bytes read and chars written, provided the output array allows for at least two characters. Also see the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.

]]></format>

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