I was asked for an example how to create a sales order through AIF document services (SalesSalesOrderService). Here is my minimalist variant in C# (for AX2012 and demo data):

var line = new AxdEntity_SalesLine()
{
    ItemId = "D0001",
    SalesQty = 42,
    SalesUnit = "ea"
};
 
var order = new AxdEntity_SalesTable()
{
    CustAccount = "US-003",
    PurchOrderFormNum = "xyz",
    ReceiptDateRequested = DateTime.Now.Date,
    SalesLine = new AxdEntity_SalesLine[] { line }
};
 
var orderList   = new AxdEntity_SalesTable[] { order };
var callContext = new CallContext() { Company = "USMF" };
var client      = new SalesOrderServiceClient();
 
try
{
    client.create(callContext, orderList);
    client.Close();
}
catch
{
    client.Abort();
    throw;
}

It doesn’t have to work for you out of the box (for example, you may have additional fields required by the contract), but it should give you an idea how it looks like, without adding unnecessary complexity.

If you’re not familiar with AIF document services, you may want to look at AX 2012 Documentation Resources for AIF and Services.