[Backport to preview2] Fix empty string binding to nullable value types#34243
Closed
StephaneDelcroix wants to merge 1 commit intorelease/11.0.1xx-preview2from
Closed
[Backport to preview2] Fix empty string binding to nullable value types#34243StephaneDelcroix wants to merge 1 commit intorelease/11.0.1xx-preview2from
StephaneDelcroix wants to merge 1 commit intorelease/11.0.1xx-preview2from
Conversation
> [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment if this change resolves your issue. Thank you! ## Description When binding `Entry.Text` to a nullable value type property (e.g., `int?`), clearing the Entry now correctly sets the property to `null` instead of retaining the previous value. ## Issue Fixes #8342 ## Root Cause In `BindingExpressionHelper.TryConvert()`, when converting an empty string to a nullable type like `int?`: 1. The underlying type was extracted (`int`) 2. `Convert.ChangeType("", int)` was called, which throws `FormatException` 3. The catch block returned `false`, keeping the old value ## Solution Added a check before `Convert.ChangeType()` to handle empty/whitespace strings when converting to nullable types. When the target type is nullable and the source is an empty/whitespace string, the value is set to `null` and the conversion succeeds. ## Behavior | Target Type | Empty String Input | Result | |-------------|-------------------|--------| | `int?`, `double?`, etc. (nullable) | `""` | `null` ✅ | | `int`, `double`, etc. (non-nullable) | `""` | Conversion fails, retains last valid value (unchanged) | ## Testing Added two unit tests in `BindingUnitTests.cs`: - `TwoWayBindingToIntPropertyWithEmptyStringRetainsLastValidValue` - Verifies non-nullable int behavior - `TwoWayBindingToNullableIntPropertyWithEmptyStringBecomesNull` - Verifies nullable int now converts to null
Contributor
There was a problem hiding this comment.
Pull request overview
Backports the binding conversion fix to release/11.0.1xx-preview2 so that clearing an Entry.Text bound TwoWay to a nullable value type (e.g., int?) correctly updates the source to null instead of retaining the previous value.
Changes:
- Update
BindingExpressionHelper.TryConvertto treat""asnullwhen converting to nullable value types. - Add unit tests covering TwoWay bindings to non-nullable and nullable numeric properties when the
Entrytext is cleared (and related scenarios).
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/Controls/src/Core/BindingExpressionHelper.cs | Adds an early-return conversion path mapping empty string to null for nullable target types. |
| src/Controls/tests/Core.UnitTests/BindingUnitTests.cs | Adds regression tests for clearing Entry.Text when bound to int, int?, and double?. |
| var entry = new Entry { BindingContext = vm }; | ||
| entry.SetBinding(Entry.TextProperty, "Value", BindingMode.TwoWay); | ||
|
|
||
| Assert.Equal("3.14", entry.Text); |
There was a problem hiding this comment.
This test hard-codes the decimal separator by asserting entry.Text equals "3.14". Since binding/string conversion uses CultureInfo.CurrentCulture, this can fail under cultures that use a comma decimal separator (e.g., pt-PT/de-DE). Set the culture explicitly for the test (e.g., InvariantCulture) or compute the expected string using the current culture (e.g., 3.14.ToString(CultureInfo.CurrentCulture)).
Suggested change
| Assert.Equal("3.14", entry.Text); | |
| Assert.Equal(3.14.ToString(CultureInfo.CurrentCulture), entry.Text); |
This was referenced Feb 25, 2026
Open
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Note
Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!
Backport of #33536 to
release/11.0.1xx-preview2.Cherry-pick of 4cc0dc5 — clean, no conflicts.