Imports System
Imports System.Text.RegularExpressions
Class Program
Public Shared Sub Main()
Dim input As String = "ab<br/><br/>cd<br/>efg<br/><br/><br/>hijk<br/><br/>"
Dim pattern As String = "(<br\s*/?>\s*)+"
Dim replacement As String = "<br/>"
Dim output As String = Regex.Replace(input, pattern, replacement)
Console.WriteLine(output)
End Sub
End Class
' run:
'
' ab<br/>cd<br/>efg<br/>hijk<br/>
'