4 – Menerapkan MVVM pada Windows Presentation Forms (WPF)

Rosa Valentine Lammora | 05111840000035 | PBKK A

Penjelasan

  • Buat project baru yang berjenis Windows Presentation Forms App dengan .NET Framework di Visual Studio 2019.

Model

  • Klik kanan pada nama proyek di Solution Explorer, kemudian klik Add Class.
  • Pertama kita membuat class ItemPenjualan yang terisi dengan deklarasi nama dan tipe dari atribut-atribut pada sebuah barang penjualan. Class ini disebut sebagai model dalam kerangka kerja MVVM. Di sini kita bisa menambahkan handling untuk ketidaksesuaian input pada form.
  • Isi file ItemPenjualan.cs dengan kode berikut:
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LatihanMVVM
{
    class ItemPenjualan
    {
        public ItemPenjualan()
        {
            DiskonPersen = 0;
        }

        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public long Id { get; set; }

        [StringLength(50)]
        public string NamaBarang { get; set; }

        public int Jumlah { get; set; }

        public decimal Harga { get; set; }

        public decimal DiskonPersen { get; set; }

        public decimal Total()
        {
            decimal total = Jumlah * Harga;
            return total - (DiskonPersen / 100 * total);
        }
    }
}

View

  • Kemudian, kita modifikasi view dengan mengklik file MainWindow.xaml. Working space kita akan menampilkan purwarupa aplikasi WPF.
  • Isi file MainWindow.xaml dengan kode berikut:
<Window x:Class="LatihanMVVM.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="356" Width="528">

    <Window.Resources>
        <Style TargetType="TextBlock">
            <Setter Property="FontSize" Value="20" />
            <Setter Property="FontFamily" Value="Myriad Pro" />
            <Setter Property="FontWeight" Value="SemiBold" />
            <Setter Property="Background">
                <Setter.Value>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FF508FC4" Offset="0" />
                        <GradientStop Color="#FF6F94AD" Offset="1" />
                        <GradientStop Color="#FFC7F3FF" Offset="0.302" />
                    </LinearGradientBrush>
                </Setter.Value>
            </Setter>
            <Setter Property="Foreground">
                <Setter.Value>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FF5252CE" Offset="0" />
                        <GradientStop Color="#FF1B1B5D" Offset="0.953" />
                        <GradientStop Color="#FF6363CB" Offset="0.337" />
                    </LinearGradientBrush>
                </Setter.Value>
            </Setter>
        </Style>

        <Style TargetType="Label">
            <Setter Property="FontSize" Value="14" />
        </Style>

        <Style TargetType="TextBox">
            <Setter Property="Language" Value="in-IN" />
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Border x:Name="customBorder" Background="{TemplateBinding Background}" CornerRadius="5" BorderThickness="2" BorderBrush="Gray">
                            <ScrollViewer x:Name="PART_ContentHost"/>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsKeyboardFocused" Value="True">
                                <Setter TargetName="customBorder" Property="Effect">
                                    <Setter.Value>
                                        <DropShadowEffect BlurRadius="5" ShadowDepth="0" Color="#578EC9"/>
                                    </Setter.Value>
                                </Setter>
                            </Trigger>
                            <Trigger Property="IsKeyboardFocused" Value="False">
                                <Setter Property="Foreground" Value="Gray" />
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <Setter Property="Validation.ErrorTemplate">
                <Setter.Value>
                    <ControlTemplate>
                        <StackPanel Orientation="Horizontal">
                            <AdornedElementPlaceholder />
                            <TextBlock Text="Perlu Diperbaiki!" Padding="3" Foreground="Red" />
                        </StackPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

        <Style TargetType="Button">
            <Setter Property="Background" Value="#DEF2FC" />
            <Setter Property="Foreground" Value="Black" />
            <Setter Property="FontSize" Value="15"/>
            <Setter Property="Effect">
                <Setter.Value>
                    <DropShadowEffect BlurRadius="3" ShadowDepth="0" Color="#578EC9"/>
                </Setter.Value>
            </Setter>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Button}">
                        <Border x:Name="customBorder" Background="{TemplateBinding Background}" CornerRadius="4" BorderThickness="2" BorderBrush="Gray">
                            <ContentPresenter Content="{TemplateBinding Content}" HorizontalAlignment="Center" />
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Setter Property="Background" Value="#2394CC" />
                                <Setter Property="Foreground" Value="White" />
                            </Trigger>
                            <Trigger Property="IsPressed" Value="True">
                                <Setter Property="Effect" Value="{x:Null}" />
                            </Trigger>
                            <Trigger Property="IsEnabled" Value="False">
                                <Setter Property="Effect">
                                    <Setter.Value>
                                        <BlurEffect Radius="3"  />
                                    </Setter.Value>
                                </Setter>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <Grid>
        <Label Content="Nama Barang:" Height="29" HorizontalAlignment="Left" Margin="0,49,0,0" Name="label2" VerticalAlignment="Top" HorizontalContentAlignment="Right" Width="107" />
        <TextBox Height="23" HorizontalAlignment="Stretch" Margin="112,55,12,0" Name="textBox1" VerticalAlignment="Top" Text="{Binding Path=NamaBarang}"/>
        
        <Label Content="Jumlah:" Height="27" HorizontalAlignment="Left" Margin="1,86,0,0" Name="label3" VerticalAlignment="Top" Width="106" HorizontalContentAlignment="Right" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="113,90,0,0" Name="textBox2" VerticalAlignment="Top" Width="62" Text="{Binding Path=Jumlah, StringFormat={}{0:#}}"/>
        
        <Label Content="Harga:" Height="28" HorizontalAlignment="Left" Margin="12,122,0,0" Name="label4" VerticalAlignment="Top" HorizontalContentAlignment="Right" Width="95" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="113,127,0,0" Name="textBox3" VerticalAlignment="Top" Width="124" Text="{Binding Path=Harga, StringFormat={}{0:C}}" />
        
        <Button Content="Simpan" Height="27" HorizontalAlignment="Left" Margin="207,228,0,0" Name="button1" VerticalAlignment="Top" Width="82" Command="{Binding SimpanCommand}"/>
        
        <Label Content="Diskon (%):" Height="33" HorizontalAlignment="Left" Margin="12,161,0,0" Name="label5" VerticalAlignment="Top" HorizontalContentAlignment="Right" Width="95" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="113,165,0,0" Name="textBox4" VerticalAlignment="Top" Width="62" Text="{Binding Path=DiskonPersen, StringFormat={}{0:#}}"/>
        
        <Label Content="Total:" Height="33" HorizontalAlignment="Left" Margin="12,194,0,0" Name="label6" VerticalAlignment="Top" HorizontalContentAlignment="Right" Width="95" />
        <Label Content="{Binding Path=Total}" Height="28" HorizontalAlignment="Left" Margin="113,194,0,0" Name="label7" VerticalAlignment="Top" Width="402" />
        
        <TextBlock Height="28" HorizontalAlignment="Stretch" Name="textBlock1" Text="Tambah Item Penjualan" VerticalAlignment="Top" TextAlignment="Center" Margin="0,12,0,0" />

        <Grid.Background>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FFB7CEFF" Offset="0.192" />
                <GradientStop Color="White" Offset="1" />
                <GradientStop Color="#FF1648AD" Offset="0" />
            </LinearGradientBrush>
        </Grid.Background>

    </Grid>
</Window>
  • Sesuaikan elemen antarmuka sedemikian rupa hingga terbentuk sebuah formulir penambahan item penjualan beserta tombol untuk menyimpan data item.

View Model

  • Kita lanjut dengan membuat view model. Pada kerangka kerja MVVM, view model berperan untuk menampung nilai/state yang ada di view sehingga operasi modifikasi terhadap nilai tersebut tidak dilakukan di view.
  • Klik Add Class dan beri nama class-nya ItemPenjualanViewModel.
  • Isi file ItemPenjualanViewModel.cs dengan kode berikut:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;

namespace LatihanMVVM
{
    class ItemPenjualanViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private ItemPenjualan model;
        private ICommand simpanCommand;

        public ICommand SimpanCommand
        {
            get
            {
                if (this.simpanCommand == null)
                {
                    this.simpanCommand = new SimpanCommand(this);
                }
                return this.simpanCommand;
            }
        }

        public ItemPenjualanViewModel(ItemPenjualan itemPenjualan = null)
        {
            this.model = itemPenjualan ?? new ItemPenjualan();
        }

        public string NamaBarang
        {
            get { return model.NamaBarang; }
            set
            {
                if (value != model.NamaBarang)
                {
                    model.NamaBarang = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("NamaBarang"));
                }
            }
        }

        public int Jumlah
        {
            get { return model.Jumlah; }
            set
            {
                if (value != model.Jumlah)
                {
                    model.Jumlah = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("Jumlah"));
                    PropertyChanged(this, new PropertyChangedEventArgs("Total"));
                }
            }
        }

        public decimal Harga
        {
            get { return model.Harga; }
            set
            {
                if (value != model.Harga)
                {
                    model.Harga = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("Harga"));
                    PropertyChanged(this, new PropertyChangedEventArgs("Total"));
                }
            }
        }

        public decimal DiskonPersen
        {
            get { return model.DiskonPersen; }
            set
            {
                if (value != model.DiskonPersen)
                {
                    model.DiskonPersen = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("DiskonPersen"));
                    PropertyChanged(this, new PropertyChangedEventArgs("Total"));
                }
            }
        }

        public string Total
        {
            get
            {
                decimal? total = model.Total();
                if (!total.HasValue)
                {
                    return "-";
                }
                else
                {
                    return total.Value.ToString("C");
                }
            }
        }

        public ItemPenjualan Model
        {
            get { return this.model; }
        }
    }

    class SimpanCommand : ICommand
    {
        private ItemPenjualanViewModel viewModel;
        public SimpanCommand(ItemPenjualanViewModel viewModel)
        {
            this.viewModel = viewModel;
        }

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return viewModel.Model.Total() > 0;
        }

        public void Execute(object parameter)
        {
            using (var db = new LatihanContext())
            {
                db.Database.Log = Console.Write;
                db.DaftarItemPenjualan.Add(viewModel.Model);
                db.SaveChanges();
                MessageBox.Show("Berhasil disimpan ke Database");
            }
        }
    }
}

Database

  • Selanjutnya, kita akan menghubungkan aplikasi ke database MySQL. Pertama, install Entity Framework melalui NuGet Package Manager. Untuk tugas ini, saya meng-install versi 6.0.0.
  • Kemudian, install MySQL Connector untuk Visual Studio di https://downloads.mysql.com/archives/c-net/. Pilih versi 6.8.x karena versi itulah yang kompatibel dengan Entity Framework versi 6.0.0. Di sini saya menggunakan versi 6.8.7.
  • Pada Solution Explorer, klik kanan pada project dan klik Add > Reference.
  • Centang MySql.Data dan MySql.Data.Entity for EF6 dari MySQL Connector 6.8.7 dan klik OK.
  • Buka file App.config, kemudian ubah isinya menjadi kode berikut (sesuaikan nama database, uid, dan password dengan database Anda):
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --></configSections>
  <connectionStrings>
    <add name="LatihanContext" connectionString="server=localhost; database=latihanmvvm_db; uid=root; password=" providerName="MySql.Data.MySqlClient" />
  </connectionStrings>
	<entityFramework>
		<providers>
			<provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6" />
			<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
		</providers>
	</entityFramework>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />	
  </startup>
</configuration>
  • Tambah class LatihanContext sebagai persistence context (data access layer) yang berisi:
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LatihanMVVM
{
    [DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))]
    class LatihanContext : DbContext
    {
        public DbSet<ItemPenjualan> DaftarItemPenjualan { get; set; }
    }
}
  • Jangan lupa untuk menyalakan MySQL melalui XAMPP Control Panel dan membuat database sesuai dengan nama database di App.config.

Build & Run

Antarmuka awal, sebelum memasukkan data
Antarmuka setelah sukses meng-input data
Isi tabel itempenjualan di phpMyAdmin pada localhost

Link Github: https://github.com/arommal/PBKK/tree/master/LatihanMVVM

By Arommal

about as hard as a megalith and as soft as the clouds.

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