There are several ways to do it. One I used is
Response.Write("<script>window.open(" + redirectURL + ",'_blank');</script>")
Another example where I populated my list with links:
Dim link As HyperLink = CType(item.Cells(0).FindControl("lnkOpenQuote"), HyperLink)
If linkedQuoteList(item.ItemIndex).BusinessLineId = Library.Constants.LineOfBusinessid.PersonalUmbrella Then
Dim redirectURL As String = "yoursiteURL"
redirectURL += "parameters if any"
link.NavigateUrl = redirectURL
link.Target = "_blank"