when I called the function:

<System.Web.Services.WebMethod()>
Public Shared Function item_selected(ByVal munit) As Integer
Dim da As New OleDbDataAdapter
Dim cmdSQL1 As OleDbCommand
m_unit = munit
SQL1 = "SELECT unit_id,code_id, code_desc FROM cpms.code_vw where unit_id= '" & m_unit & "' "
SQL1 = SQL1 & "and code_type != 2 "
cmdSQL1 = New OleDbCommand(SQL1, ConnDB)
da.SelectCommand = cmdSQL1
ds_po.Clear()
da.Fill(ds_po)
Grid2.DataSource = ds_po.Tables(0)
Grid2.DataBind()
End Function


I get an error message:

Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class.

that is happened at the line: Grid2.DataSource = ds_po.Tables(0)

would you tell me how to solve it. thanks