IDataRecord.GetBytes/GetChars should be annotated to allow a null buffer

[chrarnoldus]

The buffer parameter of GetBytes/GetChars should be annotated to allow null values. Currently in .NET 5.0.0 they are annotated to not allow null values (see #38810).

The documentation states:

If you pass a buffer that is null, GetChars returns the length of the field in characters.

Source: https://docs.microsoft.com/en-us/dotnet/api/system.data.idatarecord.getchars?view=net-5.0#remarks

In SqlClient the implementation does indeed conform to the documentation: https://github.com/dotnet/SqlClient/blob/f0572f3e9990b391d6102911fe12223e748e117b/src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlDataReader.cs#L1663

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[stephentoub]

cc: @roji

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Issue Details

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The buffer parameter of GetBytes/GetChars should be annotated to allow null values. Currently in .NET 5.0.0 they are annotated to not allow null values (see #38810).

The documentation states:

If you pass a buffer that is null, GetChars returns the length of the field in characters.

Source: https://docs.microsoft.com/en-us/dotnet/api/system.data.idatarecord.getchars?view=net-5.0#remarks

In SqlClient the implementation does indeed conform to the documentation: https://github.com/dotnet/SqlClient/blob/f0572f3e9990b391d6102911fe12223e748e117b/src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlDataReader.cs#L1663

Author:	chrarnoldus
Assignees:	-
Labels:	area-System.Data
Milestone:	-

[roji]

Yeah, this is an incorrect annotation. I've submitted #44938 to fix this; technically this is a breaking change in case someone has implemented IDataRecord directly (as opposed to via DbDataReader, which is correctly annotated).

Listed this in dotnet/docs#21202 for documentation.