[release/11.0] AppContext switch for restoring exception handling behavior in WPF Clipboard APIs - #15035
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…ipboard APIs (#15022) * Fixes empty string scenario in bug #14322 Fix: Added a new AppContext switch: "Windows.Clipboard.ThrowExceptionsForGetAPIs" When set, the Clipboard Get* APIs will throw exception during a Clipboard failure. this switch is off by default. In off state the APIs will continue to swallow exceptions and return an empty string. Added unit tests. * PR comments. * Throwing exception for QueryGetData also.
KlausLoeffelmann
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Sep 3, 2026
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Same remarks as stated in #15037.
Thanks, Shyam!!
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Backport of #15022 to release/11.0
Fixes empty string scenario in bug #14322
Description
Until .NET 9.0, the WPF Clipboard Get* APIs threw exceptions when an operation failed. This differed from the WinForms Clipboard APIs, which swallow exceptions and return an empty string.
In .NET 10, we unified the clipboard implementation in System.Private.Windows.Core. The unified implementation follows the existing WinForms behavior, but this introduces a behavior change for WPF: its Clipboard APIs now also swallow exceptions and return an empty string instead of propagating the exception.
Customer Impact
This behavior change is causing issues for some existing WPF applications that rely on exceptions being thrown to detect clipboard operation failures. More details are available in the bug.
Regression
Yes - In WPF from .NET 9.0
Fix
Added a new AppContext switch: "Windows.Clipboard.ThrowExceptionsForGetAPIs" When set, the Clipboard Get* APIs will throw exception during a Clipboard failure. This switch is off by default. In off state the APIs will continue to swallow exceptions and return an empty string.
Added unit tests.
Testing
Created a WinForms app to write unicode data on the clipboard and another app to read it. Before the changes, the reader app returned empty string very frequently. After fix and with the new AppContext switch turned on, the app did not return empty string for Get* APIs at all.
Risk
This should be a very low risk change as this behavior was working fine in 9.0 and previous versions.
Microsoft Reviewers: Open in CodeFlow