dotnet/Documentation/compatibility/system_uri-parsing-adheres-to-rfc-3987.md

System.Uri parsing adheres to RFC 3987

Scope

Major

Version Introduced

4.5

Source Analyzer Status

Available

Change Description

URI parsing has changed in several ways in .NET 4.5. Note, however, that these changes only affect code targeting .NET 4.5. If a binary targets .NET 4.0, the old behavior will be observed. Changes to URI parsing in .NET 4.5 include:

• URI parsing will perform normalization and character checking according to the latest IRI rules in RFC 3987.

• Unicode normalization form C will only be performed on the host portion of the URI.

• Invalid mailto: URIs will now cause an exception.

• Trailing dots at the end of a path segment are now preserved.

• file:// URIs do not escape the ? character.

• Unicode control characters U+0080 through U+009F are not supported.

• Comma characters , or %2c are not automatically unescaped.

• Quirked

• Build-time break

Recommended Action

If the old .NET 4.0 URI parsing semantics are necessary (they often aren't), they can be used by targeting .NET 4.0. This can be accomplished by using a xref:System.Runtime.Versioning.TargetFrameworkAttribute?displayProperty=name on the assembly, or through Visual Studio's project system UI in the 'project properties' page.

Affected APIs

• M:System.Uri.#ctor(System.String)
• M:System.Uri.#ctor(System.String,System.Boolean)
• M:System.Uri.#ctor(System.String,System.UriKind)
• M:System.Uri.#ctor(System.Uri,System.String)
• M:System.Uri.TryCreate(System.String,System.UriKind,System.Uri@)
• M:System.Uri.TryCreate(System.Uri,System.String,System.Uri@)
• M:System.Uri.TryCreate(System.Uri,System.Uri,System.Uri@)

Category

Core