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SYSLIB0031: EncodeOID is obsolete

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The CryptoConfig.EncodeOID(String) method is marked as obsolete, starting in .NET 6. Using this API in code generates warning SYSLIB0031 at compile time and throws a PlatformNotSupportedException exception at run time.

Workarounds

Use the ASN.1 functionality provided in System.Formats.Asn1.

Suppress a warning

If you must use the obsolete APIs, you can suppress the warning in code or in your project file.

To suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the warning.

// Disable the warning.
#pragma warning disable SYSLIB0031

// Code that uses obsolete API.
// ...

// Re-enable the warning.
#pragma warning restore SYSLIB0031

To suppress all the SYSLIB0031 warnings in your project, add a <NoWarn> property to your project file.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
   ...
   <NoWarn>$(NoWarn);SYSLIB0031</NoWarn>
  </PropertyGroup>
</Project>

For more information, see Suppress warnings.