I tried this code for if i have duplicate string in multiple `arraylist` it update `1_Maths,2_Maths`

e.g.
in multiplearraylist i have

> 
> maths 
> 
> 
> english 
> 
> 
> maths 
> 
> 
> hindi 
> 
> 
> english
> 
> 
> 

**so i want o/p:**

> 
> 1\_Maths
> 
> 
> 1\_english
> 
> 
> 2\_Maths hindi
> 
> 
> 2\_english
> 
> 
> 

My code is this for generate array list

```
Dim col As Integer = 0
Dim dt As New DataTable

Dim ArraySubject(0, Grd.Columns.Count - 1) As String
For i As Integer = 0 To Grd.Columns.Count - 1
   If Grd.Columns(i).Visible = True Then
      ArraySubject(0, col) = GvSearch.HeaderRow.Cells(i).Text 
      col += 1
    End If
Next

```

Answer in c# would also help me.