IEnvelope.Expand Method

Moves the X and Y coordinates of the sides toward or away from each other.

[Visual Basic 6.0]
Sub Expand(
    ByVal dx As Double, _
    ByVal dy As Double, _
    ByVal asRatio As Boolean _
)

[Visual Basic .NET]
Public Sub Expand ( _
    ByVal dx As Double, _
    ByVal dy As Double, _
    ByVal asRatio As Boolean _
)

[C#]
public void Expand (
    double dx,
    double dy,
    bool asRatio
);

[Java]
public void expand (
    double dx,
    double dy,
    Boolean asRatio
)
throws
    IOException,
    AutomationException

[C++]
HRESULT Expand(
  double dx,
  double dy,
  VARIANT_BOOL asRatio
);

[C++]

Parameters

dx is a parameter of type double

dy is a parameter of type double

asRatio

asRatio is a parameter of type VARIANT_BOOL

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

Expand scales the size of the Envelope. If asRatio = FALSE, the expansion is additive.

XMin = XMin - dx
YMin = YMin - dy
XMax = XMax + dx
YMax = YMax + dy

If asRatio = TRUE, the expansion is multiplicative.

XMin = (XMin - dx*Width)/2
YMin = (YMin - dy*Height)/2 
XMax = (XMax + dx*Width)/2
YMax = (YMax + dy*Height)/2

The Envelope remains centered at the same position.

Envelope Expand Example

EDN: ESRI Developer Network