Document Decoder.Convert exception conditions

The doc incorrectly stated in the remarks section that this method does not throw when the output buffer is too small.
In its exception section it incorrectly indicates that the output buffer must be large enough for the entire input buffer.

The correction indicates that the output buffer need only be **2 chars** in length in order to avoid the exception.

Author: AArnott

xml/System.Text/Decoder.xml

@@ -172,7 +172,7 @@ Any remaining processed data that is part of a logical unit, such as the high su
 
 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. 
+<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>
@@ -315,7 +315,7 @@ The `completed` parameter can also be set to `false`, even though the `bytesUsed
           <paramref name="chars" /> or <paramref name="bytes" /> is <see langword="null" /> (<see langword="Nothing" />).</exception>
         <exception cref="T:System.ArgumentOutOfRangeException">
           <paramref name="charCount" /> or <paramref name="byteCount" /> is less than zero.</exception>
-        <exception cref="T:System.ArgumentException">The output buffer is too small to contain any of the converted input. The output buffer should be greater than or equal to the size indicated by the <see cref="Overload:System.Text.Decoder.GetCharCount" /> method.</exception>
+        <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="~/docs/standard/base-types/character-encoding.md">Character Encoding in .NET</see>)
 
  -and-
@@ -417,7 +417,7 @@ The following example uses the <xref:System.Text.Encoder.Convert%2A> method to c
  -or-
 
  The length of <paramref name="bytes" /> - <paramref name="byteIndex" /> is less than <paramref name="byteCount" />.</exception>
-        <exception cref="T:System.ArgumentException">The output buffer is too small to contain any of the converted input. The output buffer should be greater than or equal to the size indicated by the <see cref="Overload:System.Text.Decoder.GetCharCount" /> method.</exception>
+        <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="~/docs/standard/base-types/character-encoding.md">Character Encoding in .NET</see>)
 
  -and-
@@ -898,7 +898,7 @@ The following example uses the <xref:System.Text.Encoder.Convert%2A> method to c
 
  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.
 
- 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. Also see the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
+ 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>
         </remarks>
@@ -972,7 +972,7 @@ The following example uses the <xref:System.Text.Encoder.Convert%2A> method to c
 
  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.
 
- 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 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. Also see the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
+ 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 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 the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
 
  ]]></format>
         </remarks>
@@ -1055,7 +1055,7 @@ The following example uses the <xref:System.Text.Encoder.Convert%2A> method to c
 
  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.
 
- 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 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. Also see the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
+ 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 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 the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
 
 
 
@@ -1157,7 +1157,7 @@ The following example uses the <xref:System.Text.Encoder.Convert%2A> method to c
 
  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.
 
- 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 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. Also see the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
+ 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 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 the <xref:System.Text.Encoding.GetChars%2A?displayProperty=nameWithType> topic for more comments.
 
  ]]></format>
         </remarks>