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Windows Forms obsoletions and warnings (.NET 7)

  • Article

Some Windows Forms APIs have been marked as obsolete, starting in .NET 7. Other APIs aren't obsolete but will cause a compile-time warning if you reference them.

Previous behavior

In previous .NET versions, these APIs can be used without any build warning.

New behavior

In .NET 7 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 warnings individually instead of blanket-suppressing all obsoletion warnings.

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

Diagnostic ID Description Severity Version introduced
WFDEV001 Casting to/from IntPtr is unsafe. Use WParamInternal, LParamInternal, or ResultInternal instead. Warning Preview 1
WFDEV002 System.Windows.Forms.DomainUpDown.DomainUpDownAccessibleObject is no longer used to provide accessible support for DomainUpDown controls. Use AccessibleObject instead. Warning RC 1
WFDEV003 System.Windows.Forms.DomainUpDown.DomainItemAccessibleObject is no longer used to provide accessible support for DomainUpDown items. Use AccessibleObject instead. Warning RC 1

Version introduced

.NET 7

Type of breaking change

These obsoletions and warnings can affect source compatibility.

  • Follow the specific guidance provided for the each diagnostic ID using the URL link provided on the warning.
  • If necessary, you can suppress the warning using the custom WFDEVxxx diagnostic ID value.

Affected APIs

WFDEV001

WFDEV002

WFDEV003

See also