Function Union( _
   ByVal range2 As IRange _
) As IRange

IRange Union( 
   IRange range2
)

public void RangeIntersectUnionSubtract()
{
    // Create a workbook to play with.
    IWorkbook workbook = Factory.GetWorkbook();
    IWorksheet worksheet = workbook.Worksheets[0];
    IRange cells = worksheet.Cells;
 
    // Create some ranges.
    IRange a1 = cells["A1"];
    IRange a1_b3 = cells["A1:B3"];
    IRange b3_d4 = cells["B3:D4"];
 
    // A variable to hold results.
    IRange range;
 
    // A1 does not intersect with B3:D4
    range = a1.Intersect(b3_d4);
    Debug.Assert(range == null);
 
    // Subtracting B3:D4 from A1 does not change A1.
    range = a1.Subtract(b3_d4);
    Debug.Assert(range != null && range.Address.Equals("$A$1"));
 
    // The union of A1 and B3:D4 is "A1,B3:D4".
    range = a1.Union(b3_d4);
    Debug.Assert(range != null && range.Address.Equals("$A$1,$B$3:$D$4"));
 
    // B3:D4 does not intersect with A1.
    range = b3_d4.Intersect(a1);
    Debug.Assert(range == null);
 
    // Subtracting A1 from B3:D4 does not change B3:D4.
    range = b3_d4.Subtract(a1);
    Debug.Assert(range != null && range.Address.Equals("$B$3:$D$4"));
 
    // The union of B3:D4 and A1 is "A1,B3:D4".
    range = b3_d4.Union(a1);
    Debug.Assert(range != null && range.Address.Equals("$A$1,$B$3:$D$4"));
 
    // The intersection of B3:D4 and A1:B3 is B3
    range = b3_d4.Intersect(a1_b3);
    Debug.Assert(range != null && range.Address.Equals("$B$3"));
 
    // Subtracting A1:B3 from B3:D4 leaves "C3:D3,B4:D4".
    range = b3_d4.Subtract(a1_b3);
    Debug.Assert(range != null && range.Address.Equals("$C$3:$D$3,$B$4:$D$4"));
 
    // The union of B3:D4 and A1:B3 is "A1:B2,A3:D3,B4:D4".
    range = b3_d4.Union(a1_b3);
    Debug.Assert(range != null && range.Address.Equals("$A$1:$B$2,$A$3:$D$3,$B$4:$D$4"));
 
    // The intersection of "A1,B1,A2,B2" and "A1:B1,A2:B2" is A1:B2.
    range = cells["A1,B1,A2,B2"].Intersect(cells["A1:B1,A2:B2"]);
    Debug.Assert(range != null && range.Address.Equals("$A$1:$B$2"));
}

Public Sub RangeIntersectUnionSubtract()
    ' Create a workbook to play with.
    Dim workbook As IWorkbook = Factory.GetWorkbook()
    Dim worksheet As IWorksheet = workbook.Worksheets(0)
    Dim cells As IRange = worksheet.Cells
 
    ' Create some ranges.
    Dim a1 As IRange = cells("A1")
    Dim a1_b3 As IRange = cells("A1:B3")
    Dim b3_d4 As IRange = cells("B3:D4")
 
    ' A variable to hold results.
    Dim range As IRange
 
    ' A1 does not intersect with B3:D4
    range = a1.Intersect(b3_d4)
    Debug.Assert(range Is Nothing)
 
    ' Subtracting B3:D4 from A1 does not change A1.
    range = a1.Subtract(b3_d4)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$A$1"))
 
    ' The union of A1 and B3:D4 is "A1,B3:D4".
    range = a1.Union(b3_d4)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$A$1,$B$3:$D$4"))
 
    ' B3:D4 does not intersect with A1.
    range = b3_d4.Intersect(a1)
    Debug.Assert(range Is Nothing)
 
    ' Subtracting A1 from B3:D4 does not change B3:D4.
    range = b3_d4.Subtract(a1)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$B$3:$D$4"))
 
    ' The union of B3:D4 and A1 is "A1,B3:D4".
    range = b3_d4.Union(a1)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$A$1,$B$3:$D$4"))
 
    ' The intersection of B3:D4 and A1:B3 is B3
    range = b3_d4.Intersect(a1_b3)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$B$3"))
 
    ' Subtracting A1:B3 from B3:D4 leaves "C3:D3,B4:D4".
    range = b3_d4.Subtract(a1_b3)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$C$3:$D$3,$B$4:$D$4"))
 
    ' The union of B3:D4 and A1:B3 is "A1:B2,A3:D3,B4:D4".
    range = b3_d4.Union(a1_b3)
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$A$1:$B$2,$A$3:$D$3,$B$4:$D$4"))
 
    ' The intersection of "A1,B1,A2,B2" and "A1:B1,A2:B2" is A1:B2.
    range = cells("A1,B1,A2,B2").Intersect(cells("A1:B1,A2:B2"))
    Debug.Assert(Not (range Is Nothing) And range.Address.Equals("$A$1:$B$2"))
End Sub