How to highlight the search word in asp.net ?

try this function:-

Function Highlight(vFind, vSearch)
    Dim RegEx
    Set RegEx = New RegExp
    RegEx.Pattern = vFind
    RegEx.IgnoreCase = True
    Highlight = RegEx.Replace(vSearch, "<span class=""Highlight"">" & vFind &"</span>")
    Set RegEx = Nothing
End Function

This is not about case sensitive searching, this is about showing the actual
match rather than what was being searched for. Hope that makes sense.

For example:
Response.Write Highlight("something", "Have you seen Something About
Mary?")

Gives:
Something (with highlighted).

If you want to go with jquery then see below link:-
http://hugoware.net/blog/more-jquery-magic-search-highlighting[^]
Demo[^]