`PropertyChanged` triggered on empty string
karmeye opened this issue · comments
Describe the bug
The following returns false even though both are empty strings
if (!global::System.Collections.Generic.EqualityComparer<string?>.Default.Equals(myString, value))Regression
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Steps to reproduce
1. <TextBox Text="{x:Bind MyString, Mode=TwoWay}" />
2. Leave empty and tab in and out.
3. `OnPropertyChanged` (and the other methods) is called
Expected behavior
PropertyChanged should not be triggered when the new value is an empty string for a current empty string value.
Screenshots
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IDE and version
VS 2022
IDE version
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Nuget packages
- CommunityToolkit.Common
- CommunityToolkit.Diagnostics
- CommunityToolkit.HighPerformance
- CommunityToolkit.Mvvm (aka MVVM Toolkit)
Nuget package version(s)
8.2.2
Additional context
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Help us help you
No, just wanted to report this
I copypasted the line you mentioned in a REPL console, and it works as expected. Are you sure you are not triggering something else that is causing the OnPropertyChanged to being called?
Ok, what happens is that the first time I tab out of the text box, Text (i.e. the binding) is null and this triggers PropertyChanged, as null and empty string is not considered equal. Just by tabbing in and out of the text box, the textbox changes the binding value from null to empty string. After that OnPropertyChanged is not called any more.
I guess we can remove the bug label.
I don't really want the TextBox to change the value, as it is represented as null rather than empty string in the database.
Is there a way to conditionally prevent a control from updating the binding?