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AreaBasedLoadBoundaryLineData.TopLevelId

Property
Description:
The top level id of the area based load boundary line.
Remarks:
The top level's elevation cannot be lower than the bottom level.
Syntax
public ElementId TopLevelId { get; set; }
Exceptions
Exception Condition
ArgumentException When setting this property: The ElementId levelId cannot be used as the top level. The ElementId levelId is not a Level or it's elevation is lower than the bottom level's elevation.
ArgumentNullException When setting this property: A non-optional argument was null