Nullability of type of parameter 'existingValue' doesn't match overridden member (possibly because of nullability attributes).

Nullability of type of parameter 'value' doesn't match overridden member (possibly because of nullability attributes).

Converting null literal or possible null value to non-nullable type.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Possible null reference argument for parameter 'key' in 'object? Dictionary<string, object?>.this[string key]'.

Converting null literal or possible null value to non-nullable type.