How to implement a blank operation

Blank operations are used by the partners so that they have the potential to add countless additional operations to the POS. They are triggered from the user interface and have supporting parameters. Partners can use blank operations to add functionality and operations that are missing from the LS One POS.

The default functionality of the Blank Operations dll is to display a message saying that the operation has not been implemented.

The text below will go through the implementation of a blank operation step-by-step. In this case, an operation will be created that retrieves the first retail item.

Creating a blank operation in site manager

Open the Visual Studio solution provided in the development pack.

Source > Solution.sln

Configure the solution for the current machine

Right-click on the SMStartProject project and select Properties.
Click on the Debug tab.
Check the Start external program option. And click the … button.
Navigate to the location where you put the development pack. In the development pack, navigate to the SM Build path and select Site Manager.exe.
Source > SM > Build > Site Manager.exe
Right-click on the SMStartProject and click Set as StartUp Project.

Create a new Blank operation

Select the Tools tab in the top ribbon and click on the Options.
Select the Blank operations tab and add a new blank operation.
Set the Operation name as FirstRetailItemOperation and press OK. Optionally you can set parameters for the operation that can be used when the operation is executed.

Close the Site Manager

Implementing the operation

Open the Visual Studio solution provided in the development pack.

Source > Solution.sln

Configure the solution for the current machine

Right-click on the POSStartProject project and select Properties.
Click on the Debug tab.
Check the Start external program option. And click the … button.
Navigate to the location where you put the development pack. In the development pack, navigate to the POS Build path and select POS.exe.
Source > POS > Build > LS One POS.exe
Right-click on the POSStartProject and click Set as StartUp Project.

Navigate to the BlankOperationsService project in the solution explorer

POS > Services > BlankOperationsService

Adding code to the Blank operation

Open up BlankOperationService.cs from the BlankOperationsService project.
Replace the current BlankOperation function with the following function.

public IPosTransaction BlankOperation(IConnectionManager entry, ISession session, 
									  OperationInfo operationInfo, IPosTransaction posTransaction)
{
	string comment = string.Empty;
	// Check for our new blank operation
	if(operationInfo.OperationId.Contains("FirstRetailItemOperation"))
	{
		RetailItem item = Interfaces.Services.InventoryService(entry).GetFirstRetailItem(entry);
		if(item != null)
		{
			comment = "The first retail item is: " + item.Text;
		}
		else
		{
			comment = "No retail items found.";
		}
	}
	else //Default functionality
	{
		comment = "This operation has not been implemented."
					+ "\r\n\r\n"
					+ "Operation Id received: " + operationInfo.OperationId
					+ "\r\n"
					+ "Parameter received: " + operationInfo.Parameter;
	}

	BlankOperation blankOperation = Providers.BlankOperationData.Get(entry, operationInfo.OperationId);
	Interfaces.Services.DialogService(entry).ShowMessage(comment, 
											blankOperation != null ? blankOperation.OperationDescription : "", 
											MessageBoxButtons.OK, MessageBoxIcon.Information);
    
	return posTransaction;
}

For best practice, the methods that execute the logic of the operation should not be in the blank operations dll itself, but rather in a different service solution that is responsible for the current operation.

GetFirstRetailItem function is just an example. If the methods used for the new blank operation do not exist, they must be created.
Log on to the POS.
Right-click on the button that you want to assign the blank operation to and select Button properties.
Select Blank Operation in the Operation combo box.
Select your blank operation in the Blank operation combo box.
Click on OK.
If the operation was correctly set up then a dialog with the first retail item should pop up once the blank operation button was pressed.

Exception handling and logging

The LS One POS framework provides support for trace and error logging.
The ErrorLogger in the database entry provides functionality for logging trace and error messages. The type of logging is controlled by a type enum showed in the code example below.

public void PreVoidTransaction(IConnectionManager entry
							   PreTriggerResults results,
							   PosTransaction posTransaction)
{
	try
	{
		entry.ErrorLogger.LogMessage(LogMessageType.Trace, 
									"Before voiding the transaction...",
									"TransactionTriggers.PreVoidTransaction");
	}
	catch (Exception x)
	{
		entry.ErrorLogger.LogMessage(LogMessageType.Error, this.ToString(), x);
		throw x;
	}
}

Avoiding resetting the POS layout and concluding internal transactions

If no retail transaction is created (there are no items on the transaction yet), a result callback will be called at the end of the operation, concluding the transaction and resetting the POS layout to its default state.

To avoid this, you can set the flag SkipResultCallback before returning from the BlankOperation function in the BlankOperationService.

operationInfo.SkipResultCallback = true;

An example when you might want to do this would be if you want to give the user a choice (e.g. in a message box dialog) and then open a different button menu depending on the reply from the user.

Demo operations

In the TrainingSolution of the development pack, you can find an example with multiple blank operations similar to the one below.

if (operationInfo.OperationId.ToUpper() == "NEWSHIFT") { RunNewShift(operationInfo, posTransaction); }

Below you can find a detailed description of each blank operation from the TrainingSolution.

Operation	Description
NEWSHIFT	Starts a new shift
ITEMSALE	Perform an item sale operation
PRICEOVERRIDE	Override the price of an item
PRICECHECK	Open a window where the price of an item can be checked
VOIDITEM	Void or unvoid the selected item
ITEMCOMMENT	Add a comment to the current item
SETQUANTITY	Set the quantity of the current item
CLEARQUANTITY	Reset the quantity of the current item to the default value
INVOICECOMMENT	Add an invoice comment to the transaction
CHANGEUOM	Change the unit of measurement of an item
ICONREQUEST	Request info codes for the current item
CLEARITEMCOMMENTS	Clear all comments for the current item
CHANGEITEMCOMMENTS	Change the comments for the current item
LINEDISCOUNTAMOUNT	Give a discount amount for the current item
LINEDISCOUNTPERCENT	Give a discount percent for the current item
TOTALDISCOUNTPERCENT	Give a total discount percent
TOTALDISCOUNTAMOUNT	Give a total discount amount
SUSPENDTRANSACTION	Suspend a retail transaction which can be retrieved and finished at a later time
CUSTOMERCLEAR	Clears the customer from the current transaction
LOGOFF	Perform a log off operation
LOCKTERMINAL	Locks the terminal by the current user
MINIMIZEPOS	Minimizes the POS window
ENDOFDAY	Perform an end of day operation
ENDOFSHIFT	Perform an end of shift operation
TENDERDECLARATION	Perform a tender declaration operation
DECLARESTARTAMOUNT	Perform a declare start amount operation
FLOATENTRY	Perform a float entry operation
TENDERREMOVAL	Perform a tender removal operation
SAFEDROP	Perform a safe drop operation
BANKDROP	Perform a bank drop operation
SAFEDROPREVERSAL	Perform a safe drop reversal operation
BANKDROPREVERSAL	Perform a bank drop reversal operation