I am trying to call Oracle function which return SYS_REFCURSOR from VB. I was able to retrieve data using stored procedure. Same way I tried to call oracle function but it giving an error.

Appreaciate if anyone can help ? Thanks. I'll provide screen shots if needed.

Function in DB end
====================

PKG BODY

FUNCTION GET_ALLCUST RETURN SYS_REFCURSOR AS 
  getallcursor SYS_REFCURSOR; 
BEGIN
    OPEN getallcursor FOR SELECT * FROM CUSTOMER; 
    RETURN getallcursor; 
CLOSE getallcursor;
END;

PKG Spec
==============

create or replace PACKAGE GetAllProdPckg AS
   PROCEDURE GetAllProd;
   PROCEDURE get_allprod_viasqldev;
   PROCEDURE get_allcust_viasqldev;
   FUNCTION get_allcust RETURN SYS_REFCURSOR;
   function GET_ALLPROD_FROM_DB RETURN SYS_REFCURSOR;
   
   END GetAllProdPckg;

** ERROR **

System.NullReferenceException: 'Object reference not set to an instance of an object.

MY Code =========================================================================

    Private Sub Button1_Click_1(sender As Object, e As EventArgs) Handles Button1.Click
        Dim rvConn As Oracle.DataAccess.Client.OracleConnection
        rvConn = CreateConnection()
        Dim rvCmd As New Oracle.DataAccess.Client.OracleCommand
        '  Dim OracleRefCursor As New Oracle.DataAccess.Client.OracleDbType.RefCursor
        Dim ds As DataSet

        Dim oraDataAdapter As New Oracle.DataAccess.Client.OracleDataAdapter()


        Try
            rvCmd.Connection = rvConn
            rvConn.Open()

            Dim strSQL As String
            strSQL = "getallprodpckg.get_allcust"
            rvCmd.CommandType = CommandType.StoredProcedure
            rvCmd.CommandText = strSQL
            MsgBox("")

            Dim qrySerial3 As New Oracle.DataAccess.Client.OracleParameter("getallcursor", OracleDbType.RefCursor) With {
            .Direction = ParameterDirection.Output}


            rvCmd.Parameters.Add(qrySerial3)


            Dim vStr As String
            Dim reader As OracleDataReader = rvCmd.ExecuteReader

            While reader.Read()
                Console.WriteLine("{0}", reader(0) & reader(1) & reader(2))
                MsgBox(vStr)
            End While


        Catch ex As Exception
            MessageBox.Show("ERROR OCCURRED" & ex.Message)

        Finally
            rvConn.Close()
        End Try

    End Sub

** DB connection class **

Public Class Form1 Private Sub TestOracleButton_Click(sender As Object, e As EventArgs) Handles TestOracleButton.Click TestOracleConnection() End Sub

Dim custID As Integer
Dim custID2 As Integer
Dim custName As String
Dim prodID As Integer
Dim prodName As String
Dim prodPrice As Integer
Dim prodAmount As Integer
Dim custAmount As Integer
Dim custStatus As String
Dim prodQuant As Integer

Public Sub TestOracleConnection()
    Dim rvConn As Oracle.DataAccess.Client.OracleConnection
    rvConn = CreateConnection()
    Try
        rvConn.Open()
        MessageBox.Show("Oracle Connection OK")
    Catch ex As Exception
        MessageBox.Show(ex.Message)
        MessageBox.Show("No Oracle Connection established")
    Finally
        rvConn.Close()
    End Try
End Sub
Public Function CreateConnection() As Oracle.DataAccess.Client.OracleConnection
    Dim rvConn As New Oracle.DataAccess.Client.OracleConnection With {
        .ConnectionString = GetConnectionString()
    }
    Return rvConn
End Function
Public Function GetConnectionString() As String
    Dim vConnStr As String
    vConnStr = "Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)"
    vConnStr = vConnStr & "(HOST=feenix-oracle.swin.edu.au)(PORT=1521))"
    vConnStr = vConnStr & "(CONNECT_DATA=(SERVICE_NAME=dms)));"
    vConnStr = vConnStr & "User Id=S1234564;"
    vConnStr = vConnStr & "Password=******;"
    Return vConnStr
End Function

You need to get the reader from the parameter, not from the command.

So instead of

Dim reader As OracleDataReader = rvCmd.ExecuteReader()

You need:

rvCmd.CommandType = CommandType.StoredProcedure
rvCmd.CommandText = "getallprodpckg.get_allcust"

Dim qrySerial3 As New Oracle.DataAccess.Client.OracleParameter(
    None, OracleDbType.RefCursor, ParameterDirection.ReturnValue)

rvCmd.Parameters.Add(qrySerial3)

rvCmd.ExecuteNonQuery()

Dim cursor as OracleRefCursor = DirectCast(qrySerial3.Value, OracleRefCursor)

Dim reader As OracleDataReader = cursor.GetDataReader()