Task 3: Implement the IOrderingService Interface

2010-03-05

In this task, you use the IOrderingService interface that you created in Task 2 by implementing the interface in the Simple Order Form host application to create a local service for communicating with the running workflow.

When a user submits a new order, the host application raises the NewOrder event, which is processed by the OrderProcessingWorkflow. The OrderProcessingWorkflow calls the ItemStatusUpdate method of the IOrderingService. Then it calls that method in the host application to update the user interface.

Note

Although you are encouraged to follow the exercises in a linear manner, it is not required. You can start this exercise by opening the sample project and proceeding to the steps in the following section.

Implementing the Interface

Follow these steps to implement the interface that you created in the previous task.

To implement the IOrderingService interface

Add the following component references to the StateMachineHost project:
- System.Workflow.Runtime
- System.Workflow.Activities
- System.Workflow.ComponentModel

Add the following references to the Mainform.cs file in the StateMachineHost project:

System.Workflow.Activities
System.Workflow.ComponentModel
System.Workflow.Runtime
StateMachineWorkflow

Imports System.Workflow.Activities
Imports System.Workflow.ComponentModel
Imports System.Workflow.Runtime
Imports StateMachineWorkflow

using System.Workflow.Activities;
using System.Workflow.ComponentModel;
using System.Workflow.Runtime;
using StateMachineWorkflow;

In the Mainform source file in the StateMachineHost project, derive the MainForm class from the IOrderingService interface so that the main Form itself can serve as the service class for communicating with the workflow.
```
Public Class MainForm : Inherits Form : Implements IOrderingService
End Class
```
```
public class MainForm : Form, IOrderingService
```

In the MainForm class, create an array of type string that contains some inventory items used for creating orders.

Private inventoryItems() As String = { "Apple", "Orange", 
            "Banana", "Pear", "Watermelon", "Grapes" }

private string[] inventoryItems = { "Apple", "Orange", 
            "Banana", "Pear", "Watermelon", "Grapes" };

In the MainForm class, create a delegate to handle item status updates.

Private Delegate Sub ItemStatusUpdateDelegate(orderId As Guid, newStatus As String)

private delegate void ItemStatusUpdateDelegate(Guid orderId, string newStatus);

In the MainForm class, create a new public method named ItemStatusUpdate that accepts a Guid named orderId and a String named newStatus as parameters. This method is used to change the order status, which has the effect of changing the currently active state in the workflow.
```
Public Sub ItemStatusUpdate(ByVal orderId As Guid, ByVal newStatus As String) Implements IOrderingService.ItemStatusUpdate
End Sub
```
```
public void ItemStatusUpdate(Guid orderId, string newStatus)
{
}
```
In the MainForm class, create a private WorkflowRuntime field named workflowRuntime and initialize it to null (Nothing in Visual Basic).
In the MainForm class, create an ExternalDataExchangeService field named exchangeService and initialize it to null (Nothing in Visual Basic). This service serves as a container for the custom local data exchange service that is used to communicate with the workflow.
```
private WorkflowRuntime workflowRuntime = null;
private ExternalDataExchangeService exchangeService = null;
```
In the MainForm class, create a private generic EventHandler of the NewOrderEventArgs type named newOrderEvent. This event is raised to create a new order, which has the effect of starting a new workflow instance to track the order.
In the MainForm class, create a public generic EventHandler event property of the NewOrderEventArgs type named NewOrder.

In the NewOrder event property, create an Add and Remove accessor to add and remove event handlers from the newOrderEvent event.

private event EventHandler<NewOrderEventArgs> newOrderEvent;
public event EventHandler<NewOrderEventArgs> NewOrder
{
    add
    {
        newOrderEvent += value;
    }
    remove
    {
        newOrderEvent -= value;
    }
}

Create a private Dictionary field of type string, List<string> called orderHistory. This field is used to track the running workflow instances.
```
Private orderHistory as Dictionary(Of String, List(Of String))
```
```
private Dictionary<string, List<string>> orderHistory;
```

Initialize the orderHistory object in the constructor of the Mainform class to a new instance of a Dictionary object.

orderHistory = new Dictionary(Of String, List(Of String))

orderHistory = new Dictionary<string, List<string>>();

In the MainForm constructor, create an instance of the WorkflowRuntime object after the code that creates an instance of the orderHistory object.
Create an instance of the ExternalDataExchangeService object after the code created in the previous step.
Add the ExternalDataExchangeService object to the WorkflowRuntime services by calling the AddService method and passing the exchangeService object as a parameter.
Add the MainForm object to the ExternalDataExchangeService services by calling the AddService method and passing the this (Me in Visual Basic) object as a parameter. This allows the Mainform object itself to act as a messaging service for the workflow run-time object.

Start the WorkflowRuntime by calling the StartRuntime method.

this.workflowRuntime = new WorkflowRuntime();
this.exchangeService = new ExternalDataExchangeService();
this.workflowRuntime.AddService(this.exchangeService);
this.exchangeService.AddService(this);
this.workflowRuntime.StartRuntime();

Creating the Windows Form Controls

Add the following line to the Mainform.Designer file.

Imports System.Windows.Forms
using System.Windows.Forms;

Add the following code to the Mainform class in the Mainform.Designer file. This code serves as the logic for the user interface for controlling the application. Because the focus of this tutorial is on creating and using workflows rather than Windows Forms, it is not necessary to go into details about the workings of the form. Please see MSDN for information on the operation of Windows Forms.

        Private label1 As System.Windows.Forms.Label
        Private itemsList As System.Windows.Forms.ComboBox
        Private label2 As System.Windows.Forms.Label
        Private itemQuantity As System.Windows.Forms.NumericUpDown
        Private submitButton As System.Windows.Forms.Button
        Private groupBox1 As System.Windows.Forms.GroupBox
        Private ordersIdList As System.Windows.Forms.ComboBox
        Private label3 As System.Windows.Forms.Label
        Private orderStatus As System.Windows.Forms.TextBox
        Private label4 As System.Windows.Forms.Label

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.ComboBox itemsList;
        private System.Windows.Forms.Label label2;
        private System.Windows.Forms.NumericUpDown itemQuantity;
        private System.Windows.Forms.Button submitButton;
        private System.Windows.Forms.GroupBox groupBox1;
        private System.Windows.Forms.ComboBox ordersIdList;
        private System.Windows.Forms.Label label3;
        private System.Windows.Forms.TextBox orderStatus;
        private System.Windows.Forms.Label label4;

Replace the code in the InitializeComponent method in the Mainform.Designer.cs or Mainform.Designer.vb file (hidden by default in the “Windows Form Designer Code” section) with the following code.

            Me.label1 = New System.Windows.Forms.Label()
            Me.itemsList = New System.Windows.Forms.ComboBox()
            Me.label2 = New System.Windows.Forms.Label()
            Me.itemQuantity = New System.Windows.Forms.NumericUpDown()
            Me.submitButton = New System.Windows.Forms.Button()
            Me.groupBox1 = New System.Windows.Forms.GroupBox()
            Me.orderStatus = New System.Windows.Forms.TextBox()
            Me.label4 = New System.Windows.Forms.Label()
            Me.ordersIdList = New System.Windows.Forms.ComboBox()
            Me.label3 = New System.Windows.Forms.Label()
            (Me.itemQuantity As _ System.ComponentModel.ISupportInitialize).BeginInit()
            Me.groupBox1.SuspendLayout()
            Me.SuspendLayout()
            ‘ 
            ‘ label1
            ‘ 
            Me.label1.AutoSize = true
            Me.label1.Location = New System.Drawing.Point(12, 9)
            Me.label1.Name = "label1"
            Me.label1.Size = New System.Drawing.Size(23, 13)
            Me.label1.TabIndex = 0
            Me.label1.Text = "Item"
            ‘ 
            ‘ Me.itemsList
            ‘ 
            Me.itemsList.DropDownStyle = ComboBoxStyle.DropDownList
            Me.itemsList.FormattingEnabled = true
            Me.itemsList.Location = New System.Drawing.Point(13, 26)
            Me.itemsList.Name = "itemsList"
            Me.itemsList.Size = New System.Drawing.Size(161, 21)
            Me.itemsList.TabIndex = 0
            ‘ 
            ‘ label2
            ‘ 
            Me.label2.AutoSize = true
            Me.label2.Location = New System.Drawing.Point(12, 50)
            Me.label2.Name = "label2"
            Me.label2.Size = New System.Drawing.Size(42, 13)
            Me.label2.TabIndex = 2
            Me.label2.Text = "Quantity"
            ‘ 
            ‘ Me.itemQuantity
            ‘ 
            Me.itemQuantity.Location = New System.Drawing.Point(13, 67)
            Me.itemQuantity.Minimum = New decimal(New int[] { _
            1, _
            0, _
            0, _
            0})
            Me.itemQuantity.Name = "itemQuantity"
            Me.itemQuantity.Size = New System.Drawing.Size(80, 20)
            Me.itemQuantity.TabIndex = 1
            Me.itemQuantity.Value = New decimal(New int[] { _
            1, _
            0, _
            0, _
            0})
            ‘ 
            ‘ Me.submitButton
            ‘ 
            Me.submitButton.Location = New System.Drawing.Point(99, 64)
            Me.submitButton.Name = "submitButton"
            Me.submitButton.Size = New System.Drawing.Size(100, 23)
            Me.submitButton.TabIndex = 2
            Me.submitButton.Text = "Submit Order"
            AddHandler Me.submitButton.Click, AddressOf Me.submitButton_Click
            ‘ 
            ‘ groupBox1
            ‘ 
            Me.groupBox1.Controls.Add(Me.orderStatus)
            Me.groupBox1.Controls.Add(Me.label4)
            Me.groupBox1.Controls.Add(Me.ordersIdList)
            Me.groupBox1.Controls.Add(Me.label3)
            Me.groupBox1.Location = New System.Drawing.Point(13, 93)
            Me.groupBox1.Name = "groupBox1"
            Me.groupBox1.Size = New System.Drawing.Size(247, 193)
            Me.groupBox1.TabIndex = 3
            Me.groupBox1.TabStop = false
            Me.groupBox1.Text = "Order Status"
            ‘ 
            ‘ orderStatus
            ‘ 
            Me.orderStatus.Location = New System.Drawing.Point(7, 82)
            Me.orderStatus.Multiline = true
            Me.orderStatus.Name = "orderStatus"
            Me.orderStatus.ReadOnly = true
            Me.orderStatus.Size = New System.Drawing.Size(230, 105)
            Me.orderStatus.TabIndex = 3
            ‘ 
            ‘ label4
            ‘ 
            Me.label4.AutoSize = true
            Me.label4.Location = New System.Drawing.Point(8, 65)
            Me.label4.Name = "label4"
            Me.label4.Size = New System.Drawing.Size(35, 13)
            Me.label4.TabIndex = 2
            Me.label4.Text = "History"
            ‘ 
            ‘ ordersIdList
            ‘ 
            Me.ordersIdList.DropDownStyle = ComboBoxStyle.DropDownList
            Me.ordersIdList.FormattingEnabled = true
            Me.ordersIdList.Location = New System.Drawing.Point(7, 37)
            Me.ordersIdList.Name = "ordersIdList"
            Me.ordersIdList.Size = New System.Drawing.Size(230, 21)
            Me.ordersIdList.TabIndex = 0
            AddHandler Me.ordersIdList.SelectedIndexChanged, AddressOf Me.ordersIdList_SelectedIndexChanged
            ‘ 
            ‘ label3
            ‘ 
            Me.label3.AutoSize = true
            Me.label3.Location = New System.Drawing.Point(7, 20)
            Me.label3.Name = "label3"
            Me.label3.Size = New System.Drawing.Size(41, 13)
            Me.label3.TabIndex = 0
            Me.label3.Text = "Order Id"
            ‘ 
            ‘ MainForm
            ‘ 
            Me.AcceptButton = Me.submitButton
            Me.AutoScaleDimensions = New System.Drawing.SizeF(6F, 13F)
            Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
            Me.ClientSize = New System.Drawing.Size(272, 298)
            Me.Controls.Add(Me.groupBox1)
            Me.Controls.Add(Me.submitButton)
            Me.Controls.Add(Me.itemQuantity)
            Me.Controls.Add(Me.label2)
            Me.Controls.Add(Me.itemsList)
            Me.Controls.Add(Me.label1)
            Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D
            Me.MaximizeBox = false
            Me.MinimizeBox = false
            Me.Name = "MainForm"
            Me.Text = "Simple Order Form"
            (Me.itemQuantity As System.ComponentModel.ISupportInitialize).EndInit()
            Me.groupBox1.ResumeLayout(false)
            Me.groupBox1.PerformLayout()
            Me.ResumeLayout(false)
            Me.PerformLayout()

            this.label1 = new System.Windows.Forms.Label();
            this.itemsList = new System.Windows.Forms.ComboBox();
            this.label2 = new System.Windows.Forms.Label();
            this.itemQuantity = new System.Windows.Forms.NumericUpDown();
            this.submitButton = new System.Windows.Forms.Button();
            this.groupBox1 = new System.Windows.Forms.GroupBox();
            this.orderStatus = new System.Windows.Forms.TextBox();
            this.label4 = new System.Windows.Forms.Label();
            this.ordersIdList = new System.Windows.Forms.ComboBox();
            this.label3 = new System.Windows.Forms.Label();
            ((System.ComponentModel.ISupportInitialize)(this.itemQuantity)).BeginInit();
            this.groupBox1.SuspendLayout();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(12, 9);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(23, 13);
            this.label1.TabIndex = 0;
            this.label1.Text = "Item";
            // 
            // this.itemsList
            // 
            this.itemsList.DropDownStyle = ComboBoxStyle.DropDownList;
            this.itemsList.FormattingEnabled = true;
            this.itemsList.Location = new System.Drawing.Point(13, 26);
            this.itemsList.Name = "itemsList";
            this.itemsList.Size = new System.Drawing.Size(161, 21);
            this.itemsList.TabIndex = 0;
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Location = new System.Drawing.Point(12, 50);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(42, 13);
            this.label2.TabIndex = 2;
            this.label2.Text = "Quantity";
            // 
            // this.itemQuantity
            // 
            this.itemQuantity.Location = new System.Drawing.Point(13, 67);
            this.itemQuantity.Minimum = new decimal(new int[] {
            1,
            0,
            0,
            0});
            this.itemQuantity.Name = "itemQuantity";
            this.itemQuantity.Size = new System.Drawing.Size(80, 20);
            this.itemQuantity.TabIndex = 1;
            this.itemQuantity.Value = new decimal(new int[] {
            1,
            0,
            0,
            0});
            // 
            // this.submitButton
            // 
            this.submitButton.Location = new System.Drawing.Point(99, 64);
            this.submitButton.Name = "submitButton";
            this.submitButton.Size = new System.Drawing.Size(100, 23);
            this.submitButton.TabIndex = 2;
            this.submitButton.Text = "Submit Order";
            this.submitButton.Click += new System.EventHandler(this.submitButton_Click);
            // 
            // groupBox1
            // 
            this.groupBox1.Controls.Add(this.orderStatus);
            this.groupBox1.Controls.Add(this.label4);
            this.groupBox1.Controls.Add(this.ordersIdList);
            this.groupBox1.Controls.Add(this.label3);
            this.groupBox1.Location = new System.Drawing.Point(13, 93);
            this.groupBox1.Name = "groupBox1";
            this.groupBox1.Size = new System.Drawing.Size(247, 193);
            this.groupBox1.TabIndex = 3;
            this.groupBox1.TabStop = false;
            this.groupBox1.Text = "Order Status";
            // 
            // orderStatus
            // 
            this.orderStatus.Location = new System.Drawing.Point(7, 82);
            this.orderStatus.Multiline = true;
            this.orderStatus.Name = "orderStatus";
            this.orderStatus.ReadOnly = true;
            this.orderStatus.Size = new System.Drawing.Size(230, 105);
            this.orderStatus.TabIndex = 3;
            // 
            // label4
            // 
            this.label4.AutoSize = true;
            this.label4.Location = new System.Drawing.Point(8, 65);
            this.label4.Name = "label4";
            this.label4.Size = new System.Drawing.Size(35, 13);
            this.label4.TabIndex = 2;
            this.label4.Text = "History";
            // 
            // ordersIdList
            // 
            this.ordersIdList.DropDownStyle = ComboBoxStyle.DropDownList;
            this.ordersIdList.FormattingEnabled = true;
            this.ordersIdList.Location = new System.Drawing.Point(7, 37);
            this.ordersIdList.Name = "ordersIdList";
            this.ordersIdList.Size = new System.Drawing.Size(230, 21);
            this.ordersIdList.TabIndex = 0;
            this.ordersIdList.SelectedIndexChanged += 
                new System.EventHandler(this.ordersIdList_SelectedIndexChanged);
            // 
            // label3
            // 
            this.label3.AutoSize = true;
            this.label3.Location = new System.Drawing.Point(7, 20);
            this.label3.Name = "label3";
            this.label3.Size = new System.Drawing.Size(41, 13);
            this.label3.TabIndex = 0;
            this.label3.Text = "Order Id";
            // 
            // MainForm
            // 
            this.AcceptButton = this.submitButton;
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(272, 298);
            this.Controls.Add(this.groupBox1);
            this.Controls.Add(this.submitButton);
            this.Controls.Add(this.itemQuantity);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.itemsList);
            this.Controls.Add(this.label1);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
            this.MaximizeBox = false;
            this.MinimizeBox = false;
            this.Name = "MainForm";
            this.Text = "Simple Order Form";
            ((System.ComponentModel.ISupportInitialize)(this.itemQuantity)).EndInit();
            this.groupBox1.ResumeLayout(false);
            this.groupBox1.PerformLayout();
            this.ResumeLayout(false);
            this.PerformLayout();

Initialize the itemsList combo box in the constructor for the Mainform class.

            Foreach item As String In Me.inventoryItems)
                Me.itemsList.Items.Add(item)
            Next
            Me.itemsList.SelectedIndex = 0

            foreach (string item in this.inventoryItems)
            {
                this.itemsList.Items.Add(item);
            }
            this.itemsList.SelectedIndex = 0;

Add the following methods to the MainForm class in the Mainform file.

        Private Function GetOrderHistory(orderId As String) As String
            ‘ Retrieve the order status
            Dim itemHistory As New StringBuilder()

            Foreach status As String In Me.orderHistory(orderId)
                itemHistory.Append(status)
                itemHistory.Append(Environment.NewLine)
            End Foreach
            Return itemHistory.ToString()
        End Function

        Private Sub submitButton_Click(sender As object, e As EventArgs)
        End Sub

        Private Sub ordersIdList_SelectedIndexChanged(sender as object, e As EventArgs)
            this.orderStatus.Text = GetOrderHistory(this.ordersIdList.SelectedItem.ToString())
        End Sub

        private string GetOrderHistory(string orderId)
        {
            // Retrieve the order status
            StringBuilder itemHistory = new StringBuilder();

            foreach (string status in this.orderHistory[orderId])
            {
                itemHistory.Append(status);
                itemHistory.Append(Environment.NewLine);
            }
            return itemHistory.ToString();
        }

        private void submitButton_Click(object sender, EventArgs e)
        {
        }

        private void ordersIdList_SelectedIndexChanged(object sender, EventArgs e)
        {
            this.orderStatus.Text = GetOrderHistory(this.ordersIdList.SelectedItem.ToString());
        }

Enabling New Order Processing

Next, modify the Windows Form application to enable a user to submit a new order when the Submit button is clicked. To do this, create an instance of the OrderProcessingWorkflow and run it passing in the parameters (read from the form) required to process the new order.

To submit a new order

In the submitButton_Click method, create a String variable named item and set its value equal to the SelectedItem property of the itemsList control.
Create a Int32 variable named quantity and set its value equal to the Value property of the itemQuantity control.
```
string item = this.itemsList.SelectedItem.ToString();
int quantity = (int)this.itemQuantity.Value;
```
Create a Type variable named orderWorkflow and set its value equal to the OrderProcessingWorkflow type.
Create a WorkflowInstance variable named workflowInstance and set its value equal to the return value of the CreateWorkflow method defined in the workflowRuntime object. Pass the orderWorkflow object as a parameter to the CreateWorkflow method call to create the workflow.
```
Type orderWorkflow = typeof(OrderProcessingWorkflow);
WorkflowInstance workflowInstance = this.workflowRuntime.CreateWorkflow(orderWorkflow);
```
Create a new generic List object of the String type and assign it to the orderHistory Dictionary collection, using the InstanceId of the workflowInstance object as the key. This allows the host to track the workflow instances that are created.
For the value at the orderHistory key location created in the previous step, add a String whose value is the item name and quantity that the user submitted for the order by calling the Add method defined in the Dictionary class.
```
this.orderHistory[workflowInstance.InstanceId.ToString()] = new List<string>();
this.orderHistory[workflowInstance.InstanceId.ToString()].Add
    ("Item: " + item + "; Quantity:" + quantity);
```
Call the Start method that is defined in the workflowInstance object to start the workflow.
Raise the NewOrder event, passing null (Nothing in Visual Basic) as the first parameter, and a new NewOrderEventArgs object that is initialized with the InstanceId of the workflowInstance object, the item variable and the quantity variable. This uses the local service to send a message to the workflow that a new order has been created.
```
workflowInstance.Start();

newOrderEvent(null, new NewOrderEventArgs(workflowInstance.InstanceId, item, quantity));
```

Updating the User Interface

Finally, enable the workflow to update the user interface using status messages.

To update the user interface with status messages

In the ItemStatusUpdate method, verify whether the InvokeRequired property of the ordersIdList object is true. You must perform this action because the workflow instance runs on a separate thread and updating the UI requires you to invoke operations from the UI thread.

If this property is true, create a new ItemStatusUpdateDelegate object named statusUpdate and a Object array named args that contains the orderId and newStatus parameters.

Call the Invoke method of the MainForm class, passing the statusUpdate and args objects as parameters.

If Me.ordersIdList.InvokeRequired = True Then
    Dim statusUpdate As ItemStatusUpdateDelegate = _
        New ItemStatusUpdateDelegate(AddressOf ItemStatusUpdate)
    Dim args As Object() = New Object(1) {orderId, newStatus}
    Me.Invoke(statusUpdate, args)
Else
End If

if (this.ordersIdList.InvokeRequired == true)
{
    ItemStatusUpdateDelegate statusUpdate = 
        new ItemStatusUpdateDelegate(ItemStatusUpdate);
    object[] args = new object[2] { orderId, newStatus };
    this.Invoke(statusUpdate, args);
}
else
{
}

Note

The following steps should be included in the Else body of the InvokeRequired If statement that you created in the previous step.

Create an If statement to make sure that the orderHistory collection contains a value that uses the orderId parameter as a key; this ensures that the status update is being sent to an extant list item.
In the If statement created in the previous step, set the value at the orderId key of the orderHistory collection equal to the current DateTime, with the value of the newStatus parameter appended to it.
Create a nested If statement in the If statement created in step 3 to verify whether the ordersIdList contains the orderId in its Items collection.

If it does not, add the value of the orderId to the Items collection.
Set the SelectedItem property of the orderIdList equal to the String value of the orderId parameter.

Set the Text property of the orderStatus object equal to the return value of the GetOrderHistory method. Pass the String value of the orderId object as a parameter to the GetOrderHistory method.

if (this.orderHistory.ContainsKey(orderId.ToString()))
{
    this.orderHistory[orderId.ToString()].Add
        (DateTime.Now + " - " + newStatus);

    // Update order status data UI info
    if (this.ordersIdList.Items.Contains(orderId.ToString()) == false)
    {
        this.ordersIdList.Items.Add(orderId.ToString());
    }

    this.ordersIdList.SelectedItem = orderId.ToString();
    this.orderStatus.Text = GetOrderHistory(orderId.ToString());
}

Compiling the Code

For more information about compiling your code, see Compiling the Code.

In Task 4: Define the WaitingForOrder State, you define the first state in the OrderProcessingWorkflow by adding child activities.

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Task 3: Implement the IOrderingService Interface

Implementing the Interface

To implement the IOrderingService interface

Creating the Windows Form Controls

Enabling New Order Processing

To submit a new order

Updating the User Interface

To update the user interface with status messages

Compiling the Code

See Also

Reference

Concepts

Other Resources

Additional resources