API obsoletions with non-default diagnostic IDs (.NET 6)

Some APIs have been marked as obsolete, starting in .NET 6. This breaking change is specific to APIs that have been marked as obsolete with a custom diagnostic ID. Suppressing the default obsoletion diagnostic ID, which is CS0618 for the C# compiler, does not suppress the warnings that the compiler generates when these APIs are used.

Change description

In previous .NET versions, these APIs can be used without any build warning. In .NET 6 and later versions, use of these APIs produces a compile-time warning or error with a custom diagnostic ID. The use of custom diagnostic IDs allows you to suppress the obsoletion warnings individually instead of blanket-suppressing all obsoletion warnings.

The following table lists the custom diagnostic IDs and their corresponding warning messages for obsoleted APIs.

Diagnostic ID Description Severity
SYSLIB0013 Uri.EscapeUriString(String) can corrupt the Uri string in some cases. Consider using Uri.EscapeDataString(String) for query string components instead. Warning
SYSLIB0014 WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete. Use HttpClient instead. Warning
SYSLIB0015 DisablePrivateReflectionAttribute has no effect in .NET 6+. Warning
SYSLIB0016 Use the Graphics.GetContextInfo overloads that accept arguments for better performance and fewer allocations. Warning
SYSLIB0017 Strong-name signing is not supported and throws PlatformNotSupportedException. Warning
SYSLIB0018 Reflection-only loading is not supported and throws PlatformNotSupportedException. Warning
SYSLIB0019 The System.Runtime.InteropServices.RuntimeEnvironment members SystemConfigurationFile, GetRuntimeInterfaceAsIntPtr(Guid, Guid), and GetRuntimeInterfaceAsObject(Guid, Guid) are no longer supported and throw PlatformNotSupportedException. Warning
SYSLIB0020 JsonSerializerOptions.IgnoreNullValues is obsolete. To ignore null values when serializing, set DefaultIgnoreCondition to JsonIgnoreCondition.WhenWritingNull. Warning
SYSLIB0021 Derived cryptographic types are obsolete. Use the Create method on the base type instead. Warning
SYSLIB0022 The Rijndael and RijndaelManaged types are obsolete. Use Aes instead. Warning
SYSLIB0023 RNGCryptoServiceProvider is obsolete. To generate a random number, use one of the RandomNumberGenerator static methods instead. Warning
SYSLIB0024 Creating and unloading AppDomains is not supported and throws an exception. Warning
SYSLIB0025 SuppressIldasmAttribute has no effect in .NET 6+. Warning
SYSLIB0026 X509Certificate and X509Certificate2 are immutable. Use the appropriate constructor to create a new certificate. Warning
SYSLIB0027 PublicKey.Key is obsolete. Use the appropriate method to get the public key, such as GetRSAPublicKey(). Warning
SYSLIB0028 X509Certificate2.PrivateKey is obsolete. Use the appropriate method to get the private key, such as RSACertificateExtensions.GetRSAPrivateKey(X509Certificate2), or use the X509Certificate2.CopyWithPrivateKey(ECDiffieHellman) method to create a new instance with a private key. Warning
SYSLIB0029 ProduceLegacyHmacValues is obsolete. Producing legacy HMAC values is no longer supported. Warning
SYSLIB0030 HMACSHA1 always uses the algorithm implementation provided by the platform. Use a constructor without the useManagedSha1 parameter. Warning
SYSLIB0031 CryptoConfig.EncodeOID(String) is obsolete. Use the ASN.1 functionality provided in System.Formats.Asn1. Warning
SYSLIB0032 Recovery from corrupted process state exceptions is not supported; HandleProcessCorruptedStateExceptionsAttribute is ignored. Warning
SYSLIB0033 Rfc2898DeriveBytes.CryptDeriveKey(String, String, Int32, Byte[]) is obsolete and is not supported. Use PasswordDeriveBytes.CryptDeriveKey(String, String, Int32, Byte[]) instead. Warning
SYSLIB0034 CmsSigner(CspParameters) is obsolete. Use an alternative constructor instead. Warning
SYSLIB0035 SignerInfo.ComputeCounterSignature() is obsolete. Use the overload that accepts a CmsSigner instead. Warning

Version introduced

.NET 6

  • Follow the specific guidance provided for the each diagnostic ID using the URL link provided on the warning.

  • Warnings or errors for these obsoletions can't be suppressed using the standard diagnostic ID for obsolete types or members; use the custom SYSLIBxxxx diagnostic ID value instead.

Affected APIs
























See also