Symbol used to indicate when vertex is snapped in Z.
[Visual Basic .NET] Public Property ZSnapSymbol As IMarkerSymbol
[C#] public IMarkerSymbol ZSnapSymbol {get; set;}
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Remarks
Use this property to change the symbol displayed when the editor snaps to a particular snap agent in Z coordinate space. The Z snap symbol is displayed if you are working with an edit sketch that is Z-aware and the Z-snapping is set. The ZSnapSymbol is identical to the editor's SnapSymbol by default; if SnapTips (IEditProperties2::SnapTips) are enabled, the Z-value of the snapped location is added to the SnapTip when displayed.
The snap agent knows to draw the snap symbol twice, once to get rid of the old symbol and once to draw the symbol at its new location. When setting the symbol, don't forget to set its ROP property (on the ISymbol interface) to esriROPNotXOrPen. This setting allows the symbol to erase itself when drawn twice in the same location.