Replace NET8_0_OR_GREATER with NET across all source files

[Copilot]

Since .NET 8.0 is now the minimum supported version (as defined by NetCoreAppMinimum = net8.0 in Directory.Build.props), the conditional compilation symbol NET8_0_OR_GREATER can be simplified to NET throughout the codebase.

Changes Made

This PR systematically replaces all 258 occurrences of NET8_0_OR_GREATER across 114 source files with the simpler NET symbol. The changes include:

• #if NET8_0_OR_GREATER → #if NET
• #if !NET8_0_OR_GREATER → #if !NET
• #elif NET8_0_OR_GREATER → #elif NET
• #endif // NET8_0_OR_GREATER → #endif // NET
• #endif // !NET8_0_OR_GREATER → #endif // !NET

Rationale

The replacement is safe because:

1. For .NET targets: The NET symbol is defined for .NET 5+ and since we now require .NET 8.0 minimum, any .NET target will be .NET 8.0 or greater
2. For .NET Standard/Framework targets: Neither NET8_0_OR_GREATER nor NET are defined, so the conditional compilation behavior remains unchanged

Examples

Before:

#if NET8_0_OR_GREATER
[Obsolete("Legacy formatter", DiagnosticId = "SYSLIB0051")]
#endif
protected MyException(SerializationInfo info, StreamingContext context) : base(info, context) { }

After:

#if NET
[Obsolete("Legacy formatter", DiagnosticId = "SYSLIB0051")]
#endif
protected MyException(SerializationInfo info, StreamingContext context) : base(info, context) { }

Affected Libraries

The changes span across many core libraries including:

• Microsoft.Bcl.TimeProvider
• System.Text.Json
• System.Diagnostics.EventLog
• System.Reflection.Metadata
• Various exception classes and serialization-related code

Verification

• All occurrences have been successfully replaced (0 remaining)
• Libraries build successfully with the changes
• No functional behavior changes - this is purely a conditional compilation symbol cleanup

Fixes #109226.

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[am11]

@copilot, these two as well:

src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Base64Helper/Base64Helper.cs:#if NET8_0
src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/DefaultJsonTypeInfoResolver.Helpers.cs:#if NET8_0

[jkotas]

these two as well:

@am11 NET8_0 != NET8_0_OR_GREATER. I do not think it would be correct that change these.

[Copilot]

Pull Request Overview

This PR systematically replaces all 258 occurrences of the conditional compilation symbol NET8_0_OR_GREATER with NET across 114 source files. This is a cleanup change that takes advantage of the fact that .NET 8.0 is now the minimum supported version, making the simpler NET symbol equivalent to NET8_0_OR_GREATER in all supported scenarios.

Key changes:

• Replacement of #if NET8_0_OR_GREATER with #if NET throughout the codebase
• Corresponding updates to #if !NET8_0_OR_GREATER → #if !NET
• Updates to comment references in #endif statements

Reviewed Changes

Copilot reviewed 115 out of 115 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tasks/Common/JoinedString.cs	Updates conditional compilation for interpolated string handlers
src/libraries/System.Windows.Extensions/src/System/Media/SoundPlayer.cs	Updates obsolete attribute conditional compilation
src/libraries/System.Threading.Tasks.Dataflow/src/Internal/DataflowEtwProvider.cs	Updates conditional compilation for event logging
src/libraries/System.Threading.RateLimiting/src/System/Threading/RateLimiting/DefaultPartitionedRateLimiter.cs	Updates ConfigureAwait options conditional compilation
src/libraries/System.Threading.Channels/src/System/Threading/Channels/ChannelClosedException.netcoreapp.cs	Updates exception serialization attributes
src/libraries/System.Text.Json/src/System/Text/Json/Writer/JsonWriterHelper.cs	Updates UTF-8 validation and encoding conditionals
src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/VersionConverter.cs	Updates span allocation for version formatting
src/libraries/System.Text.Json/src/System/Text/Json/Reader/JsonReaderHelper.cs	Updates search values and line counting logic
src/libraries/System.Text.Json/src/System/Text/Json/JsonException.cs	Updates exception serialization attributes
src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexParseException.cs	Updates exception serialization attributes
Various System.Security.* libraries	Updates exception serialization attributes across security components
Various System.DirectoryServices.* libraries	Updates exception serialization attributes for directory services
Various configuration and data libraries	Updates exception serialization and utility method conditionals
Test files	Updates test conditional compilation for .NET version-specific features

[agocke]

/ba-g test was disabled and tracked in #114912

[jkotas]

/ba-g test was disabled and tracked in #114912

[xtqqczze]

Some of these directives could have been removed entirely, see #118421 for context. It looks like Copilot may have overlooked that detail.