passing double values via c#

I am trying to make a purchaseorder via the sdk with c#.net.

Everything works fine but when i try to pass a quantity or a price as a double (eg 2.34) i lose the digits behind the comma.(i tried the same in vb.net, there it works but i'd prefer c#.)

Here is the code:

SAPbobsCOM.Documents oOrder = (SAPbobsCOM.Documents)oCompany.GetBusinessObject SAPbobsCOM.BoObjectTypes.oPurchaseOrders);
				
oOrder.DocObjectCode = SAPCOM.BoObjectTypes.oPurchaseOrders;
			
oOrder.HandWritten = SAPbobsCOM.BoYesNoEnum.tNO;
oOrder.DocDate = System.DateTime.Now;
oOrder.DocDueDate = System.DateTime.Now;
oOrder.CardCode = "30005";
					  
oOrder.Lines.ItemCode = "581330g";
oOrder.Lines.ItemDescription = "abcd";
oOrder.Lines.Quantity = 1.5
oOrder.Lines.Price = 2.34;

int iRetCode = oOrder.Add();

if (iRetCode != 0)
{
    //... errors
} 
else
{
    //... wrote order to database
}

thanks for any help