Request for clarification on value taking from owner and ability to unset a local value

[ite-klass]

When is the value retrieved from the parent? On construction? On property access?

Is it possible to "unset" the ambient property so that it will no longer use a (temporary) local value but the parents again? (e.g. for temporarily setting Form.Cursor to WaitCursor and then returning to using the parents)

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Document Details

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• ID: a19792a8-cf3a-ccb9-e346-6d8db28de034
• Version Independent ID: 26385aee-80b5-9df5-ba0e-6a9c0b679d17
• Content: AmbientProperties Class (System.Windows.Forms)
• Content Source: xml/System.Windows.Forms/AmbientProperties.xml
• Product: .net
• GitHub Login: @dotnet-bot
• Microsoft Alias: dotnet-bot

[mairaw]

@merriemcgaw @Tanya-Solyanik can you help with this question?

[KlausLoeffelmann]

A value different from its Parent is only stored on assignment. When there is no dedicated value set, the Parent's property value is taken in the Get Accessor of the Ambient's property.

Usually, for example with the Font property, you can set the value to null (Nothing in VB) to reset it to the Parent's value. For Color Properties, you could set the Properties to Color.Empty. Rule of thumb here is: Set the Ambient Property's value to its default value to let it reflect its Parent property again. Like:

contactListView.Font = default(Font);
contactListView.BackColor = default(Color);

In Visual Basic, when you assign Nothing, you are always assigning the Default value (which happens to be Null for Reference Types). So instead of default, in VB simply use … = Nothing, which is best practice for Value Types.

TIP: From C# 7.1 on you can omit the Type with default when it can be inferred from the context. Simply … = default; will do.

HTH

Klaus

[mairaw]

Thanks Klaus. @KlausLoeffelmann do you think we need to improve the docs in respect to that?