如何从 UserControl1 WPF MVVM 中的按钮将数据从一个 UserControl1 传递到 UserControl2

Question

I recently started studying about User Controls. I have a Main Window which contains this 2 User Controls. UserControl1 is a form to get the data, and when the submit button is clicked in UserControl1, the UserControl2 will be visible viewing the data send from the UserControl1.

Here is my MainWindow xaml (HomeCareMain.xaml)

    <Window x:Class="PatientRecordMVVM.Views.HomeCareMain"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
        FontFamily="{materialDesign:MaterialDesignFont}"
        xmlns:local="clr-namespace:PatientRecordMVVM.Views"
        mc:Ignorable="d"
        Title="HomeCareMain" Height="850" Width="1500" Foreground="White">
    <Window.Resources>
        <Storyboard x:Key="MenuOpen">
            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Width)" Storyboard.TargetName="GridSideMenu">
                <EasingDoubleKeyFrame KeyTime="0" Value="60"/>
                <EasingDoubleKeyFrame KeyTime="0:0:0:0" Value="210"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
        <Storyboard x:Key="MenuClose">
            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Width)" Storyboard.TargetName="GridSideMenu">
                <EasingDoubleKeyFrame KeyTime="0" Value="210"/>
                <EasingDoubleKeyFrame KeyTime="0:0:0:0" Value="60"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
    </Window.Resources>

    <Window.Triggers>
        <EventTrigger RoutedEvent="ButtonBase.Click" SourceName="ButtonOpenMenu">
            <BeginStoryboard Storyboard="{StaticResource MenuOpen}"/>
        </EventTrigger>
        <EventTrigger RoutedEvent="ButtonBase.Click" SourceName="ButtonCloseMenu">
            <BeginStoryboard Storyboard="{StaticResource MenuClose}"/>
        </EventTrigger>
    </Window.Triggers>

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="3*"/>
            <ColumnDefinition Width="8*"/>
            <ColumnDefinition Width="8*"/>
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition Height="2*"/>
            <RowDefinition Height="25*"/>
        </Grid.RowDefinitions>

        <Image x:Name="Logo" Grid.Row="1" Grid.ColumnSpan="3"  Source="/PatientRecordMVVM;component/Images/logo.jpg" Opacity="0.12" HorizontalAlignment="Center" VerticalAlignment="Center"/>
        <Grid Grid.Row="0" Grid.ColumnSpan="3" Height="60" VerticalAlignment="Top" Background="#2c8a93">
            <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
                <Image Source="/PatientRecordMVVM;component/Images/logo.jpg" Width="30" Height="30" Margin="0,0,20,0"/>
                <TextBlock Text="HOME CARE" FontSize="22" Foreground="White" HorizontalAlignment="Center" VerticalAlignment="Center"/>
            </StackPanel>
            <materialDesign:PopupBox PlacementMode="BottomAndAlignRightEdges" StaysOpen="False" Foreground="White" HorizontalAlignment="Right" VerticalAlignment="Center" Margin="10">
                <StackPanel Width="150">
                    <Button Content="Settings"/>
                    <Separator/>
                    <Button Command="{Binding Path=LogoutCommand}" Content="Logout"/>
                </StackPanel>
            </materialDesign:PopupBox>
        </Grid>

        <Grid x:Name="GridSideMenu" Grid.RowSpan="2" Grid.Column="0" Width="210" HorizontalAlignment="Left" Background="#1f3e66">
            <StackPanel Orientation="Vertical">
                <Grid Height="60" VerticalAlignment="Top">
                    <Button x:Name="ButtonCloseMenu" Background="{x:Null}" BorderBrush="{x:Null}" Width="60" Height="60" HorizontalAlignment="Right" Visibility="Collapsed" Click="ButtonCloseMenu_Click">
                        <materialDesign:PackIcon Kind="ArrowLeft" Width="25" Height="25"/>
                    </Button>
                    <Button x:Name="ButtonOpenMenu" Background="{x:Null}" BorderBrush="{x:Null}" Width="60" Height="60" HorizontalAlignment="Right" Click="ButtonOpenMenu_Click">
                        <materialDesign:PackIcon Kind="Menu" Width="25" Height="25"/>
                    </Button>
                </Grid>
                <ListView Foreground="White" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
                    <ListViewItem Height="60">
                        <Button Command="{Binding Path=AddPatientCommand}" CommandParameter="{Binding ElementName=AddPatient}" Background="#1f3e66" BorderBrush="#1f3e66" Width="190" Height="40" VerticalAlignment="Top">
                            <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
                                <materialDesign:PackIcon Kind="Add" Foreground="White" Width="25" Height="25" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="-5,0,20,0"/>
                                <TextBlock Text="Add Patient Details" FontSize="12" VerticalAlignment="Center" Margin='0,0,20,0'/>
                            </StackPanel>
                        </Button>
                    </ListViewItem>
                </ListView>
            </StackPanel>
        </Grid>

        <Grid Grid.Row="1" Grid.ColumnSpan="3">
            <local:AddPatientRecordDetails 
                x:Name="AddPatient" 
                HorizontalAlignment="Stretch"
                VerticalAlignment="Center"
                Width="800"
                Height="730"
                Margin="0,0,20,0"
             />
        </Grid>

        <Grid Grid.Row="1" Grid.Column="2">
            <local:PrintPreviewControl
                x:Name="PrintPreview"
                HorizontalAlignment="Center"
                Width="600"
                Height="700"
                />
        </Grid>
    </Grid>
</Window>

This is UserControl1 xaml (AddPatientRecordDetails.xaml)

<UserControl x:Class="PatientRecordMVVM.Views.AddPatientRecordDetails"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
             FontFamily="{materialDesign:MaterialDesignFont}"
             xmlns:local="clr-namespace:PatientRecordMVVM.Views"
             mc:Ignorable="d" 
             d:DesignHeight="850" d:DesignWidth="600" Background="Transparent" BorderBrush="#58af9d" BorderThickness="1">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="2.5*"/>
            <ColumnDefinition Width="3*"/>
            <ColumnDefinition Width="2.5*"/>
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition Height="1.5*"/>
            <RowDefinition Height="1.5*"/>
            <RowDefinition Height="18*"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>

        <Grid Grid.RowSpan="2" Grid.ColumnSpan="3" Background="#2c8a93"/>

        <!--Patient Id block-->
        <StackPanel Grid.ColumnSpan="2" Style="{StaticResource StackpanelStyle}">
            <Label FontSize="16" FontWeight="Bold" Foreground="White">
                Patient ID :
            </Label>
            <Label Content="{Binding Path=GuidGenerator}" FontSize="16" Foreground="White" Margin="5,0"/>
        </StackPanel>

        <!--Date block-->
        <StackPanel  Grid.ColumnSpan="3"  Style="{StaticResource StackpanelStyle}" HorizontalAlignment="Right">
            <Label FontSize="16" FontWeight="Bold" Foreground="White">
                Date :
            </Label>
            <Label Name="date_time" Content="{Binding Path=CurrentDate}" FontSize="16" Foreground="White" Margin="5,0"/>
        </StackPanel>

        <!--Title block-->
        <TextBlock Grid.Row="1" Grid.ColumnSpan="3" FontSize="20" FontWeight="Bold" Foreground="White" TextDecorations="Underline" HorizontalAlignment="Center" VerticalAlignment="Center" MinWidth="200">
                Patient Registration Information
        </TextBlock>

        <!--Main sub Grid-->
        <Grid Grid.Row="2" Grid.ColumnSpan="3" HorizontalAlignment="Stretch"  VerticalAlignment="Stretch" Margin="25,25,25,0">

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="200*" MinWidth="158" MaxWidth="190" />
                <ColumnDefinition Width="700*" MaxWidth="600" />
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Grid.RowDefinitions>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="2.95*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="2*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
                <RowDefinition Height="1*"/>
            </Grid.RowDefinitions>

            <!--Name block-->
            <Label Grid.Row="0" Grid.Column="1" Style="{StaticResource LabelStyles}">Name :</Label>
            <TextBox Name="fName" Grid.Row="0" Grid.Column="2" Text="{Binding Path = PatientName}" Style="{StaticResource TextBoxStyle}"/>

            <!--Address block-->
            <Label Grid.Row="1" Grid.Column="1" Style="{StaticResource LabelStyles}" VerticalAlignment="Top"  Margin="0,7,15,0">Address :</Label>
            <StackPanel Grid.Row="1" Grid.Column="2" Orientation="Vertical" VerticalAlignment="Center"  Margin="0,2">
                <DockPanel LastChildFill="True" Margin="0,5">
                    <Label Style="{StaticResource AddressLabelStyles}" HorizontalAlignment="Right">Number :</Label>
                    <TextBox Name="Number" Text="{Binding Path =  PatientAddress.Number}" Style="{StaticResource TextBoxStyle}"/>
                </DockPanel>
                <DockPanel LastChildFill="True" Margin="0,5">
                    <Label Style="{StaticResource AddressLabelStyles}" Margin="12,0">Street :</Label>
                    <TextBox Name="Street" Text="{Binding Path =  PatientAddress.Street}" Style="{StaticResource TextBoxStyle}" Margin="3,0,0,0" />
                </DockPanel>
                <DockPanel LastChildFill="True" Margin="0,5">
                    <Label Style="{StaticResource AddressLabelStyles}" Margin="24,0">City :</Label>
                    <TextBox Name="City" Text="{Binding Path = PatientAddress.City}" Style="{StaticResource TextBoxStyle}" Margin="-9,0,0,0"/>
                </DockPanel>
            </StackPanel>

            <!--Gender block-->
            <Label  Grid.Row="2" Grid.Column="1" Style="{StaticResource LabelStyles}">Gender :</Label>
            <StackPanel Grid.Row="2" Grid.Column="2" Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="0,6,0,0">
                <RadioButton Name="male" Command="{Binding Path=GetPatientGenderCommand}" CommandParameter="{Binding ElementName=male, Path=Content}" Content="Male" FontSize="14" Foreground="Black" Padding="5,-2.5" MinWidth="100"/>
                <RadioButton Name="female" Command="{Binding Path=GetPatientGenderCommand}" CommandParameter="{Binding ElementName=female, Path=Content}" Content="Female" FontSize="14" Foreground="Black" Padding="5,-2.5"/>
            </StackPanel>

            <!--Birthdate block-->
            <Label Grid.Row="3" Grid.Column="1" Style="{StaticResource LabelStyles}">Birthdate :</Label>
            <DatePicker Name="Date" Grid.Row="3" Grid.Column="2" SelectedDate ="{Binding Path = PatientDateOfBirth}" Style="{StaticResource TextBoxStyle}" MaxHeight="30" Padding="1"/>

            <!--Age block-->
            <Label Grid.Row="4" Grid.Column="1" Style="{StaticResource LabelStyles}">Age :</Label>
            <TextBox  Name="Age" Grid.Row="4" Grid.Column="2" Text="{Binding Path = PatientAge}" Style="{StaticResource TextBoxStyle}"/>

            <!--Image block-->
            <Label Grid.Row="5" Grid.Column="1" Style="{StaticResource LabelStyles}">Image :</Label>
            <DockPanel Grid.Row="5" Grid.Column="2" LastChildFill="True" VerticalAlignment="Center" MinHeight="30">
                <Button DockPanel.Dock="Left" Command="{Binding Path=GetPatientImageCommand, UpdateSourceTrigger=PropertyChanged}" Style="{StaticResource ButtonStyle}" Content="Browse" Margin="0,0,5,0"/>
                <TextBox Name="FileBrowser" DockPanel.Dock="Right" Text="{Binding Path= PatientImageSource}" Style="{StaticResource TextBoxStyle}" HorizontalAlignment="Stretch"/>
            </DockPanel>

            <!--Image view block-->
            <Image Name="ImageViewer" Grid.Row="6" Grid.Column="2" Source ="{Binding Path= PatientImageSource}" HorizontalAlignment="Left" MinWidth="95" MaxWidth="150" MinHeight="95" MaxHeight="150" Margin="0,0,0,10"/>

            <!--Department block-->
            <Label Grid.Row="7" Grid.Column="1" Style="{StaticResource LabelStyles}">Department :</Label>
            <ComboBox Name="Department" Grid.Row="7" Grid.Column="2" ItemsSource="{Binding Department}" SelectedItem="{Binding Path = PatientDepartment}" FontSize="14" Foreground="Black" BorderBrush="LightGray" BorderThickness="1" VerticalAlignment="Center" MinHeight="30"/>

            <!--Ward Block-->
            <Label Grid.Row="8" Grid.Column="1" Style="{StaticResource LabelStyles}">Ward :</Label>
            <ComboBox Name="Ward" Grid.Row="8" Grid.Column="2" ItemsSource="{Binding Ward}" SelectedItem="{Binding Path = PatientWard}" FontSize="14" Foreground="Black" BorderBrush="LightGray" BorderThickness="1" VerticalAlignment="Center" MinHeight="30"/>

            <!--Doctor Block-->
            <Label  Grid.Row="9" Grid.Column="1" Style="{StaticResource LabelStyles}">Doctor In Charge :</Label>
            <ComboBox Name="Doctor" Grid.Row="9" Grid.Column="2" ItemsSource="{Binding DocInCharge}" SelectedItem="{Binding Path = PatientDotorcInCharge}" FontSize="14" Foreground="Black" BorderBrush="LightGray" BorderThickness="1" VerticalAlignment="Center" MinHeight="30"/>
        </Grid>

        <!--Buttons Section-->
        <StackPanel Grid.Row="3" Grid.ColumnSpan="3" Orientation="Horizontal" HorizontalAlignment="Right" VerticalAlignment="Top" Margin="20,10,26,0" >
            <Button Command="{Binding Path=PreviewCommand}" Style="{StaticResource ButtonStyle}" Content="Print Preview" Margin="0,0,5,0"/>
            <Button Command="{Binding Path=ClearPatientCommand}" Style="{StaticResource ButtonStyle}" Content="Clear"/>
        </StackPanel>
    </Grid>
</UserControl>

This is my UserControl2 (PrintPreviewControl.xaml)

<UserControl x:Class="PatientRecordMVVM.Views.PrintPreviewControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
             FontFamily="{materialDesign:MaterialDesignFont}"
             xmlns:local="clr-namespace:PatientRecordMVVM.Views"
             mc:Ignorable="d" 
             d:DesignHeight="850" d:DesignWidth="800" Background="White">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="22*"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>

        <!--Main Sub Grid 1-->
        <Grid x:Name="MainSubGrid" Grid.Row="0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="2.5*"/>
                <ColumnDefinition Width="3*"/>
                <ColumnDefinition Width="2.5*"/>
            </Grid.ColumnDefinitions>

            <Grid.RowDefinitions>
                <RowDefinition Height ="1.5*"/>
                <RowDefinition Height ="1.5*"/>
                <RowDefinition Height ="6.5*"/>
                <RowDefinition Height ="7*"/>
                <RowDefinition Height ="6*"/>
            </Grid.RowDefinitions>

            <Grid Grid.RowSpan="2" Grid.ColumnSpan="3" Background="#58af9d"/>

            <!--Patient Id block-->
            <StackPanel Grid.ColumnSpan="2" Style="{StaticResource StackpanelStyle}">
                <Label FontSize="16" FontWeight="Bold" Foreground="White">
                    Patient ID :
                </Label>
                <Label Content="{Binding PatientID}" FontSize="16" Foreground="White" Margin="5,0,0,0"/>
            </StackPanel>

            <!--Date block-->
            <StackPanel Grid.ColumnSpan="3" Style="{StaticResource StackpanelStyle}" HorizontalAlignment="Right">
                <Label FontSize="16" FontWeight="Bold" Foreground="White">
                    Date :
                </Label>
                <Label Name="date_time" Content="{Binding PatientRegisteredDate}" FontSize="16" Foreground="White" Margin="5,0"/>
            </StackPanel>

            <!--Title block-->
            <TextBlock Grid.Row="1" Grid.ColumnSpan="3" FontSize="20" FontWeight="Bold" Foreground="White" TextDecorations="Underline" HorizontalAlignment="Center" VerticalAlignment="Center">
                Patient Registration Information
            </TextBlock>

            <!--Sub grid 1-->
            <Grid Grid.Row="2" Grid.ColumnSpan="3" HorizontalAlignment="Center" VerticalAlignment="Stretch" Margin="25,10,25,20">

                <!--User's image View and name-->
                <StackPanel Orientation="Vertical" HorizontalAlignment="Center" VerticalAlignment="Center">
                    <Ellipse Width="150" Height="150">
                        <Ellipse.Fill>
                            <ImageBrush x:Name="ImageViewer2" ImageSource="{Binding PatientImageSource}"/>
                        </Ellipse.Fill>
                    </Ellipse>
                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Left" Margin="0,10">
                        <Label Style="{StaticResource LabelStyles}" Margin="0">Patient Name :</Label>
                        <TextBlock x:Name="ViewName" Text="{Binding PatientName}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>
                </StackPanel>
            </Grid>

            <!--Sub grid 2-->
            <GroupBox Grid.Row="3" Grid.ColumnSpan="3" HorizontalAlignment="Stretch"  VerticalAlignment="Center" Margin="25,-35,25,0">
                <GroupBox.Header>
                    <TextBlock Style="{StaticResource TextBlockStyleControl}">Patient Personal Information</TextBlock>
                </GroupBox.Header>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="500*"/>
                        <ColumnDefinition Width="500*"/>
                    </Grid.ColumnDefinitions>

                    <Grid.RowDefinitions>
                        <RowDefinition Height="5*"/>
                        <RowDefinition Height="3*" MaxHeight="80"/>
                    </Grid.RowDefinitions>

                    <StackPanel Grid.Row="0" Grid.Column="0" Orientation="Vertical" Margin="10,5">
                        <Label Style="{StaticResource PreviewLabelStyles}" >Address :</Label>
                        <TextBlock x:Name="ViewANum" Text="{Binding PatientAddress.Number}" Style="{StaticResource TextBlockStyle}"/>
                        <TextBlock x:Name="ViewAStrt" Text="{Binding PatientAddress.Street}" Style="{StaticResource TextBlockStyle}"/>
                        <TextBlock x:Name="ViewACity" Text="{Binding PatientAddress.City}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>

                    <StackPanel Grid.Row="0" Grid.Column="1" Orientation="Vertical" Margin="50,5,10,10">
                        <Label  Style="{StaticResource PreviewLabelStyles}">Gender :</Label>
                        <TextBlock x:Name="ViewGender" Text="{Binding PatientGender}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>

                    <StackPanel Grid.Row="1" Grid.Column="0" Orientation="Vertical" Margin="10,5">
                        <Label  Style="{StaticResource PreviewLabelStyles}">Date of Birth :</Label>
                        <TextBlock x:Name="ViewDob" Text="{Binding PatientDateOfBirth}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>

                    <StackPanel Grid.Row="1" Grid.Column="1" Orientation="Vertical" Margin="50,5,10,5">
                        <Label Style="{StaticResource PreviewLabelStyles}">Age :</Label>
                        <TextBlock x:Name="ViewAge" Text="{Binding PatientAge}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>
                </Grid>
            </GroupBox>

            <!--Sub grid 3-->
            <GroupBox Grid.Row="4" Grid.ColumnSpan="3" HorizontalAlignment="Stretch" VerticalAlignment="Center" Margin="25,0,25,0">
                <GroupBox.Header>
                    <TextBlock Style="{StaticResource TextBlockStyleControl}">Patient Medical Information</TextBlock>
                </GroupBox.Header>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="500*"/>
                        <ColumnDefinition Width="500*"/>
                    </Grid.ColumnDefinitions>

                    <Grid.RowDefinitions>
                        <RowDefinition Height="3*"/>
                        <RowDefinition Height="3*" />
                    </Grid.RowDefinitions>

                    <StackPanel Grid.Row="0" Grid.Column="0" Orientation="Vertical" Margin="10,5">
                        <Label Style="{StaticResource PreviewLabelStyles}">Department :</Label>
                        <TextBlock x:Name="ViewDepartment" Text="{Binding PatientDepartment}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>

                    <StackPanel Grid.Row="0" Grid.Column="1" Orientation="Vertical" Margin="50,5,10,0">
                        <Label  Style="{StaticResource PreviewLabelStyles}">Ward :</Label>
                        <TextBlock x:Name="ViewWard" Text="{Binding PatientWard}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>

                    <StackPanel Grid.Row="1" Grid.Column="0" Orientation="Vertical" Margin="10,5,10,10">
                        <Label  Style="{StaticResource PreviewLabelStyles}">Doctor in Charge :</Label>
                        <TextBlock x:Name="ViewDoc" Text="{Binding PatientDotorcInCharge}" Style="{StaticResource TextBlockStyle}"/>
                    </StackPanel>
                </Grid>
            </GroupBox>
        </Grid>
        <StackPanel Grid.Row="2" Grid.ColumnSpan="3" Orientation="Horizontal" HorizontalAlignment="Right" VerticalAlignment="Top" Margin="20,10,26,0">
            <Button Command="{Binding Path=DefaultPrintCommand}" CommandParameter="{Binding ElementName=MainSubGrid}" Style="{StaticResource ButtonStyle}" Content="Default Print" Margin="0,0,5,0"/>
            <Button Command="{Binding Path=ConfigureAndPrintCommand}" CommandParameter="{Binding ElementName=MainSubGrid}" Style="{StaticResource ButtonStyle}" Content="Configure Print"/>
        </StackPanel>
    </Grid>
</UserControl>

This is the Button Command of the UserControl1 in its ViewModel

    #region Handlers : Commands
    private void OnPreviewCommandExecute()
    {
        PatientRecordDetailsModel getPatientDetails = PopulatePatientDetails();

    }

I didn't put the whole code inside the ViewModel since it's too long.

PatientRecordDetailsModel is the model object that will be sent to the UserControl2.

Inside the UserControl2 ViewModel constructor it binds the data with the userControl View.

class PrintPreviewViewModel
    {
        #region Fields
        private IWindowService m_windowService;
        private PatientRecordDetailsModel patient;
        #endregion

        #region Constructors
        public PrintPreviewViewModel(PatientRecordDetailsModel patient)
        {
            this.patient = patient;

            PatientID = patient.PatientId;
            PatientRegisteredDate = patient.PatientRegisteredDate;
            PatientName = patient.PatientName;
            PatientAddress = patient.PatientAddress;
            PatientGender = patient.PatientGender;
            PatientDateOfBirth = patient.PatientDateOfBirth.ToShortDateString();
            PatientAge = patient.PatientAge;
            PatientImageSource = patient.PatientImageSource;
            PatientDepartment = patient.PatientDepartment;
            PatientWard = patient.PatientWard;
            PatientDotorcInCharge = patient.PatientDoctorInCharge;

            m_windowService = new WindowService();
        }
       }

Inside the HomeCareMain.xaml.cs file I defined a method called PrintPreviewButtonClicked() to bind the data to the UserControl2's DataContext and to Visible it.

public partial class HomeCareMain : Window
    {
        public HomeCareMain()
        {
            InitializeComponent();
            this.DataContext = new HomeCareMainViewModel();
            PatientRecordDetailsViewModel patientRecordDetailsViewModel = new PatientRecordDetailsViewModel();           
            AddPatient.DataContext = patientRecordDetailsViewModel;
            AddPatient.Visibility = Visibility.Hidden;
            PrintPreview.Visibility = Visibility.Hidden;
        }

        public void PrintPreviewButtonClicked(PatientRecordDetailsModel patient)
        {
            PrintPreview.DataContext = new PrintPreviewViewModel(patient);
            PrintPreview.Visibility = Visibility.Visible;
        }
     }

The problem is I want to send the PatientRecordDetailsModel object to the HomeCareMain.xaml.cs without violating MVVM architecture.

Or is there an alternative way of doing this.

I have used separate viewModels for user controls and the main window since they have their own responsibilities to perform.

I really hope you could help me with this.

Answer 1

You should either bind to the same view model from both UserControls , or use an event aggregator or messenger to send an event or a message from one component to another in a loosely coupled way as explained in this blog post.

If you don't use a framework, you'll have to implement the event aggregator yourself.