Simple MVVM Toolkit 之 Messaging（B）发送消息，并接收回调

继续上一篇《Simple MVVM Toolkit 之 Messaging（A）》。

接下来使用Messaging实现客户列表View-Model和客户明细View-Model之间的通讯。

1. 为 Messaging 准备辅助类和窗体：

1.1 右键Models文件夹，添加类 MessageTokens，此类目的是提供一个消息标识符。

1.2 右键Models文件夹，添加类 IncreaseInfo，此类是一个增量信息的实体。

    public class IncreaseInfo
    {
        public IncreaseInfo()
        { }

        public IncreaseInfo(string customerName, int age)
        {
            // TODO: Complete member initialization
            this.CustomerName = customerName;
            this.Age = age;
        }

        public string CustomerName { get; set; }

        public int Age { get; set; }
    }

1.3 右键Models文件夹，添加类 ApprovalInfo，此类表示的是弹出提示窗口的消息实体。

    public class ApprovalInfo
    {
        public ApprovalInfo()
        { }

        public ApprovalInfo(string customerName, int age, bool result)
        {
            this.CustomerName = customerName;
            this.Age = age;
            this.Result = result;
        }

        public string CustomerName { get; set; }

        public int Age { get; set; }

        public bool Result { get; set; }
    }

1.4 右键Views文件夹，添加窗体 ApprovalIncrease，此窗体是一个提示框。

<Window x:Class="MessagingSimple.Views.ApprovalIncrease"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="ApproveIncrease" Height="174" Width="352">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="81*" />
            <RowDefinition Height="54*" />
        </Grid.RowDefinitions>
        
        <StackPanel Orientation="Horizontal">
            <StackPanel.Resources>
                <Style TargetType="TextBlock">
                    <Setter Property="VerticalAlignment" Value="Center" />
                </Style>
            </StackPanel.Resources>
            <TextBlock Text="Do you approve the increase of " />
            <TextBlock Name="quantityText" />
            <TextBlock Text=" for " />
            <TextBlock Name="customerText" />
            <TextBlock Text="?" />
        </StackPanel>
        <Button Content="No"
                Height="23"
                HorizontalAlignment="Left"
                Margin="202,12,0,0"
                Name="btnNo"
                VerticalAlignment="Top"
                Width="75"
                Click="btnNo_Click"
                Grid.Row="1" />
        <Button Content="Yes"
                Height="23"
                HorizontalAlignment="Left"
                Margin="73,12,0,0"
                Name="btnYes"
                VerticalAlignment="Top"
                Width="75"
                Click="btnYes_Click"
                Grid.Row="1" />
    </Grid>
</Window>

    /// <summary>
    /// ApproveIncrease.xaml 的交互逻辑
    /// </summary>
    public partial class ApprovalIncrease : Window
    {
        public ApprovalIncrease()
        {
            InitializeComponent();
        }
        public ApprovalIncrease(IncreaseInfo increaseInfo)
            : this()
        {
            this.quantityText.Text = increaseInfo.Age.ToString();
            this.customerText.Text = increaseInfo.CustomerName;
        }

        private void btnYes_Click(object sender, RoutedEventArgs e)
        {
            this.DialogResult = true;
        }

        private void btnNo_Click(object sender, RoutedEventArgs e)
        {
            this.DialogResult = false;
        }




    }

2 在Views-CustomerList.xaml中增加按钮和消息栏。

        <Button Content="Increase Age"
                Height="23"
                Grid.Row="1"
                HorizontalAlignment="Center"
                Command="{Binding Path=IncreaseAgeCommand}"
                VerticalAlignment="Center"
                Width="120"
                Margin="0,21,0,81" />
        <TextBlock Grid.Row="1"
                   Height="42"
                   HorizontalAlignment="Center"
                   Margin="0,61,0,0"
                   Name="textBlock1"
                   Text="{Binding Path=MessageText}"
                   VerticalAlignment="Top"
                   Width="245" />

3 实现 Messaging 通讯五步骤：

3.1 第一步：定义通讯标识。（MessageTokens.cs）

        //Step 1 定义增长年龄标识。
        public const string IncreaseAge = "AgeIncreaseToken";

3.2 第二步：当年龄增加之后获取通知的Register。(CustomerDetailViewModel.cs)

            //Step 2 当年龄增加之后获取通知的Register。
            RegisterToReceiveMessages<IncreaseInfo, ApprovalInfo>(
                MessageTokens.IncreaseAge, OnOrdersIncrease);

3.3 第三步：处理客户列表年龄增加的通知消息。(CustomerDetailViewModel.cs)

        //Step 3 处理客户列表年龄增加的通知消息。
        private void OnOrdersIncrease(object sender, NotificationEventArgs
           <IncreaseInfo, ApprovalInfo> e)
        {
            if (e.Data.CustomerName != Customer.CustomerName)
                return;
            ApprovalIncrease approvalIncrease = new ApprovalIncrease(e.Data);

            approvalIncrease.Closed += (s, ea) =>
            {
                ApprovalInfo approvalInfo = new ApprovalInfo(
                    Customer.CustomerName,
                    e.Data.Age,
                    (bool)approvalIncrease.DialogResult);

                e.Completed(approvalInfo);
            };

            approvalIncrease.ShowDialog();
        }

3.4 第四步：发送消息。(CustomerListViewModel.cs)

            //Step 4
            SendMessage(MessageTokens.IncreaseAge,
                new NotificationEventArgs<IncreaseInfo, ApprovalInfo>(
                    null, increaseInfo, OnIncreaseResponse));

3.5 第五步：处理通知回调。

        //Step 5 处理通知回调。
        void OnIncreaseResponse(ApprovalInfo approve)
        {
            string resultText = approve.Result ? "approved" : "rejected";
            MessageText = string.Format(
                "Age quantity of {0} {1} for {2}",
                approve.Age, resultText, approve.CustomerName);

            if (!approve.Result)
            {
                SelectedCustomer.Age -= 1;
            }
        }

流程如下：

运行效果如下。

点击这里下载源代码。(MessagingSimple-MessagingEnd)