error: imports system.data cannot b found..

hi i am using vb.net
i am trying to create a dll from a class.vb. when i am trying to create the dll from the vs.net command prompt i get this error messages:

error: namespace or type OleDb for imports system.data cannot be found:

can someone please help.. thanks

my code is as follows

VB Code:

Imports System
Imports System.Data
Imports System.Data.OleDb
Imports System.Reflection
Namespace DataLayer
    Public Class DataObj
        Private _mconn As String
 
        Public Sub New()
            MyBase.new()
            _mconn = ""
        End Sub
 
        Public Sub New(ByVal mconn As String)
            MyBase.new()
            _mconn = mconn
        End Sub
 
 
        Public Property GetConStr() As String
            Get
                Return _mconn
            End Get
            Set(ByVal Value As String)
                _mconn = Value
            End Set
        End Property
 
        Public Function GetCategories() As DataView
            Dim connstr As System.Data.OleDb.OleDbConnection
            Dim adapt As System.Data.OleDb.OleDbDataAdapter
            Dim ds As System.Data.DataSet
 
            connstr = New System.Data.OleDb.OleDbConnection(_mconn)
            adapt = New System.Data.OleDb.OleDbDataAdapter("SELECT DISTINCT CategoryName FROM Category", connstr)
            ds = New DataSet
            Try
                adapt.Fill(ds, "Category")
                Return ds.Tables("Category").DefaultView
            Catch ex As Exception
                Throw ex
            End Try
            connstr.Close()
        End Function
 
        Public Function GetProductsForCategory(ByVal category As String) As DataView
            Dim connstr As System.Data.OleDb.OleDbConnection
            Dim adapt As System.Data.OleDb.OleDbDataAdapter
            Dim ds As System.Data.DataSet
 
            connstr = New OleDbConnection(_mconn)
            adapt = New OleDbDataAdapter("SELECT ProductName,UnitPrice,ImagePath,c.CategoryId FROM Products p,Category c WHERE c.categoryId='" & category & " ' and p.CategoryId = c.CategoryId ", connstr)
            ds = New DataSet
 
            Try
                adapt.Fill(ds, "Product")
                Return ds.Tables("Product").DefaultView
            Catch ex As Exception
                Throw ex
            End Try
 
            connstr.Close()
        End Function
    End Class
 
End Namespace