dotnet/Documentation/compatibility/wpf-nullreferenceexception-in-exception-handling-code-from-imagesourceconverter_convertfrom.md

## NullReferenceException in exception handling code from ImageSourceConverter.ConvertFrom

### Scope
Edge

### Version Introduced
4.7

### Source Analyzer Status
NotPlanned

### Change Description

An error in the exception handling code for
<xref:System.Windows.Media.ImageSourceConverter.ConvertFrom(System.ComponentModel.ITypeDescriptorContext,System.Globalization.CultureInfo,System.Object)>
caused an incorrect <xref:System.NullReferenceException?displayProperty=name> to
be thrown instead of the intended exception (e.g.
<xref:System.DirectoryNotFoundException?displayProperty=name>,
<xref:System.IO.FileNotFoundException?displayProperty=name>), this change
corrects that error so that the method now throws the right exception.

By default all applications targeting .NET Framework 4.6.2 and below will
continue to throw <xref:System.NullReferenceException?displayProperty=name> for
compatibility, developers targeting .NET Framework 4.7 and above should see the
right exceptions.

// Replace the space with an 'x' if applicable
- [x] Quirked
- [ ] Build-time break

### Recommended Action

Developers who wish to revert to getting
<xref:System.NullReferenceException?displayProperty=name> when targeting .NET
Framework 4.7 can add/merge the following to their application's App.config
file:

```xml
<configuration>
    <runtime>
        <AppContextSwitchOverrides value="Switch.System.Windows.Media.ImageSourceConverter.OverrideExceptionWithNullReferenceException=true"/>
    </runtime>
</configuration>
```

### Affected APIs
- `M:System.Windows.Media.ImageSourceConverter.ConvertFrom(System.ComponentModel.ITypeDescriptorContext,System.Globalization.CultureInfo,System.Object)`

### Category
Windows Presentation Foundation (WPF)

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### Original Bug
223209
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