Sub SetDataTable_To_CSV(ByVal dtable As DataTable, ByVal path_filename As String, ByVal sep_char As String)
        Dim writer As System.IO.StreamWriter
        Try
            writer = New System.IO.StreamWriter(path_filename)

            Dim _sep As String = ""
            Dim builder As New System.Text.StringBuilder
            For Each col As DataColumn In dtable.Columns
                builder.Append(_sep).Append(col.ColumnName)
                _sep = sep_char
            Next
            writer.WriteLine(builder.ToString())

            For Each row As DataRow In dtable.Rows
                _sep = ""
                builder = New System.Text.StringBuilder

                For Each col As DataColumn In dtable.Columns
                    builder.Append(_sep).Append(row(col.ColumnName))
                    _sep = sep_char
                Next
                writer.WriteLine(builder.ToString())
            Next
        Catch ex As Exception

        Finally
            If Not writer Is Nothing Then writer.Close()
        End Try
    End Sub

This is how you use it

Dim dt As New DataTable
SetDataTable_To_CSV(dt, "C:\test.csv", ",")