Setting PNG image metadata doesn't work

Code example doesn't work. TrySave method is called before the changes in metadata.
If we add saving after the changes, the TrySave method returns false.

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#### Document Details

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* ID: 476ff378-df63-0a54-8a1b-4b8c9dc54c67
* Version Independent ID: f8e5a0e6-da8f-ccab-8dec-7d7cbe00c497
* Content: [How to: Write Metadata to a Bitmap - WPF .NET Framework](https://learn.microsoft.com/en-us/dotnet/desktop/wpf/graphics-multimedia/how-to-write-metadata-to-a-bitmap?view=netframeworkdesktop-4.8)
* Content Source: [dotnet-desktop-guide/framework/wpf/graphics-multimedia/how-to-write-metadata-to-a-bitmap.md](https://github.com/dotnet/docs-desktop/blob/main/dotnet-desktop-guide/framework/wpf/graphics-multimedia/how-to-write-metadata-to-a-bitmap.md)
* Product: **dotnet-framework**
* Technology: **dotnet-wpf**
* GitHub Login: @adegeo
* Microsoft Alias: **adegeo**