Chinese garbled problem in asp.net

Imports System.Math
Function URLEncoding(ByVal vstrIn As String)
   Dim strReturn As String
   strReturn = ""
   Dim i As Integer
   Dim ThisChr As String
   Dim innerCode, Hight8, Low8 As Integer
   For i = 1 To vstrIn.Length
       ThisChr = Mid(vstrIn, i, 1)
          If Abs(Asc(ThisChr)) < &HFF Then
                strReturn = strReturn & ThisChr
          Else
                 innerCode = Asc(ThisChr)
           If innerCode < 0 Then
                innerCode = innerCode + &H10000
           End If
           Hight8 = (innerCode And &HFF00) / &HFF
           Low8 = innerCode And &HFF
           strReturn = strReturn & "%" & Hex(Hight8) & "%" & Hex(Low8)
      End If
 Next
 URLEncoding = strReturn
End Function