Dynamics GP 2010 Web Service Question

I am trying to create a purchase order in Dynamics GP 2010 using the webservices. I get the following error VendorItemNumber not setup for ItemKey First off, I am not sure what that error actually means. Second off, I am not sure why I am getting it. My code is below. Any suggestions?

Public Sub PO()
    Dim context As Context
    Dim purchaseOrderKey As PurchaseTransactionKey
    Dim vendorKey As VendorKey
    Dim purchaseOrder As PurchaseOrder
    Dim purchaseOrderLine As PurchaseOrderLine
    Dim warehouseKey As WarehouseKey
    Dim quantityOrdered As Quantity
    Dim purchaseOrderCreatePolicy As Policy

    context = gpr.ws.getContext()

    '// Create a purchase transaction key to identify the purchase order
    purchaseOrderKey = New PurchaseTransactionKey()
    purchaseOrderKey.Id = poId

    '// Create a vendor key object to specify the vendor
    vendorKey = New VendorKey()
    vendorKey.Id = "SYN001"

    '// Create a purchase order object
    purchaseOrder = New PurchaseOrder()

    '// Populate the required properties
    purchaseOrder.Key = purchaseOrderKey
    purchaseOrder.VendorKey = vendorKey

    '// Create a purchase order line object for the purchase order object
    purchaseOrderLine = New PurchaseOrderLine()

    '// Create a quantity object to specify the quantity ordered
    quantityOrdered = New Quantity()
    quantityOrdered.Value = 1

    '// Add the quantity to the purchase order line object
    purchaseOrderLine.QuantityOrdered = quantityOrdered

    '// Specify the inventory item being purchased
    purchaseOrderLine.VendorItemNumber = dvi1

    Dim itemKey As ItemKey = New ItemKey()
    itemKey.Id = dvi1
    purchaseOrderLine.ItemKey = itemKey

    '// Create an array to hold the purchase orde开发者_StackOverflow中文版r line object
    Dim lines As PurchaseOrderLine() = New PurchaseOrderLine() {purchaseOrderLine}

    '// Add the array of purchase order lines to the purchase order object
    purchaseOrder.Lines = lines

    '// Get the create policy for purchase order objects
    purchaseOrderCreatePolicy = gpr.GetWebService.GetPolicyByOperation("CreatePurchaseOrder", context)

    '// Create the purchase order
    gpr.GetWebService.CreatePurchaseOrder(purchaseOrder, context, purchaseOrderCreatePolicy)
End Sub

In Dynamics GP, an item must be associated to a vendor before it can be purchased from that vendor. You should add a call to the CreateItemVendor method in order to associate the item with the vendor prior to creating a purchase order for it.

Code sample below:

        CompanyKey companyKey;
        Context context;
        ItemVendor itemVendor;
        ItemKey itemKey;
        VendorKey vendorKey;
        ItemVendorKey itemVendorKey;
        Policy itemVendorCreatePolicy;

        // Create an instance of the service
        DynamicsGPClient wsDynamicsGP = new DynamicsGPClient();

        // Create a context with which to call the service
        context = new Context();

        // Specify which company to use (sample company)
        companyKey = new CompanyKey();
        companyKey.Id = (-1);

        // Set up the context object
        context.OrganizationKey = (OrganizationKey)companyKey;

        // Create an item vendor object
        itemVendor = new ItemVendor();

        // Create an item key to specify the item
        itemKey = new ItemKey();
        itemKey.Id = "128 SDRAM";

        // Create a vendor key to specify the vendor
        vendorKey = new VendorKey();
        vendorKey.Id = "ACETRAVE0001";

        // Create an item vendor key
        itemVendorKey = new ItemVendorKey();
        itemVendorKey.ItemKey = itemKey;
        itemVendorKey.VendorKey = vendorKey;

        // Populate the item vendor objects key property
        itemVendor.Key = itemVendorKey;

        // Get the create policy for item vendor
        itemVendorCreatePolicy = wsDynamicsGP.GetPolicyByOperation("CreateItemVendor", context);

        // Create the item vendor
        wsDynamicsGP.CreateItemVendor(itemVendor, context, itemVendorCreatePolicy);

        // Close the service
        if(wsDynamicsGP.State != CommunicationState.Faulted)
        {
            wsDynamicsGP.Close();
        }

just go to GP interface and map this item to the vendor you are creating purchase order for and make entry in inventory for it. then try again !