IValueConverter does not support nullable contexts

_This issue has been moved from [a ticket on Developer Community](https://developercommunity.visualstudio.com/t/IValueConverter-does-not-support-nullabl/10485692)._

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System.Windows.Data.IValueConverter is also available in nullable contexts.

interface IValueConverter {
public object Convert(object value, Type targetType, object parameter, CultureInfo culture);
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture):
}

However, the value and parameter arguments across the Convert(), ConvertVack() functions can be NULL, and the return value can also be NULL.

interface IValueConverter {
public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture);
public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture):
}

It must be.

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### Original Comments

#### Feedback Bot on 10/8/2023, 06:47 AM:

(private comment, text removed)
#### Feedback Bot on 2/5/2024, 00:15 PM:

(private comment, text removed)

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### Original Solutions
(no solutions)