Вопрос, вероятно, по стилю оформления диаграммы.
Что если...
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@startuml
class BaseViewModel {
+ event PropertyChangedEventHandler PropertyChanged
# OnPropertyChanged([CallerMemberName] string PropertyName = null):void {abstract}
# Set<T>(ref T field, T value, [CallerMemberName] string PropertyName = null):bool {abstract}
}
class MainViewModel {
+ MainViewModel()
}
class Entity1ViewModel {
+ Main(args: string[]): void
}
class Entity2ViewModel {
+ Main(args: string[]): void
}
class Entity3ViewModel {
+ Main(args: string[]): void
}
BaseViewModel <|-- MainViewModel
BaseViewModel <|-- Entity1ViewModel
BaseViewModel <|-- Entity2ViewModel
BaseViewModel <|-- Entity3ViewModel
Entity1ViewModel "_entity1ViewModel" <-- MainViewModel
Entity2ViewModel "_entity2ViewModel" <-- MainViewModel
Entity3ViewModel "_entity3ViewModel" <-- MainViewModel
@enduml
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![](http://www.plantuml.com/plantuml/png/dP5HIyCm4CVVyocE-TBXzc3xLgeCny2Ngk3mPGovBhSQkAQIf9KnzzrjfQXBHt6-XNz-lylTPMOT6bSLB3QCri8jMdfMz9wMaXZs0k0Ig2RjuD6KRsJSRlwAEYUvQCCxr9B9-7UDTG4Fsak3rHoveLCgCZBtMD0Qh3DAvzz-6y8rw8fv7DUbah37h65mumvVHP_89SkRmD0Mbh1Ln7BI76haYYPmPlsiBFbt_OFeTf2YqluEZh9W_0Clj5DkTtMA3z3aDkvwMAt7CRGZ-MhuVpKwJnNUxoOVq-dnO2S9Vy81A1o6_Aw5wAzlz49UD8AatsVtNjyB_-95VIyQz6QaPLNm9m00)