public class StandardInvoiceGenerator : InvoiceGenerator 
{ 
    public override dynamic Generate() 
    { 
        return new object(); 
    } 
} 
public class StandardInvoiceAmountCalculator : AmountCalculator 
{ 
    public override decimal Calculate(dynamic item) 
    { 
        return 1; 
    } 
} 
public class PrepaymentInvoiceGenerator : InvoiceGenerator 
{ 
    public override dynamic Generate() 
    { 
        return new object(); 
    } 
} 
public class PrepaymentInvoiceAmountCalculator : AmountCalculator 
{ 
    public override decimal Calculate(dynamic item) 
    { 
        return 1; 
    } 
}

چرا چنین بویی به راه می‌افتد 

دلایل بوجود آمدن چنین بویی به سه دسته تقسیم می‌شوند: 

public interface IInvoiceGenerator 
{ 
    dynamic Generate(); 
} 
public interface IAmountCalculator 
{ 
    decimal Calculate(dynamic item); 
} 
public class StandardInvoiceGenerator : IInvoiceGenerator, IAmountCalculator 
{ 
    public dynamic Generate() 
    { 
        return new object(); 
    } 
    public decimal Calculate(dynamic item) 
    { 
        return 1; 
    } 
} 
public class PrepaymentInvoiceGenerator : IInvoiceGenerator, IAmountCalculator 
{ 
    public dynamic Generate() 
    { 
        return new object(); 
    } 
    public decimal Calculate(dynamic item) 
    { 
        return 1; 
    } 
}

public abstract class InvoiceGenerator 
{ 
    public abstract dynamic Generate(); 
    public abstract decimal CalculateItemAmount(dynamic item); 
} 
public class StandardInvoiceGenerator : InvoiceGenerator 
{ 
    public override dynamic Generate() 
    { 
        throw new NotImplementedException(); 
    } 
    public override decimal CalculateItemAmount(dynamic item) 
    { 
        throw new NotImplementedException(); 
    } 
} 
public class PrepaymentInvoiceGenerator : InvoiceGenerator 
{ 
    public override dynamic Generate() 
    { 
        throw new NotImplementedException(); 
    } 
    public override decimal CalculateItemAmount(dynamic item) 
    { 
        throw new NotImplementedException(); 
    } 
}

public List<People> ComboBoxDataSource{get; set;}

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow"
        x:Name="this">
    <Grid>
        <DataGrid ItemsSource="{Binding DataCollection}">
            <DataGrid.Columns>
                <DataGridComboBoxColumn ItemsSource="{Binding DataContext.ComboBoxDataSource, ElementName=this}"/>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

  <DataGridComboBoxColumn DisplayMemberPath="FirstName">
        <DataGridComboBoxColumn.EditingElementStyle>
              <Style TargetType="ComboBox">
                     <Setter Property="ItemsSource" Value="{Binding DataContext.ComboBoxDataSource , ElementName=this}"/>
               </Style>
         </DataGridComboBoxColumn.EditingElementStyle>
   </DataGridComboBoxColumn>

 public class DataBindingHelper : Freezable
    {
        protected override Freezable CreateInstanceCore()
        {
            return new DataBindingHelper();
        }
        public object Data
        {
            get { return (object)GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register("Data", typeof(object), typeof(DataBindingHelper), new UIPropertyMetadata(null));
    }

<DataGrid.Resources>
       <local:DataBindingHelper x:Key="bindingHelper"Data="{Binding}"/>
</DataGrid.Resources>

<DataGridComboBoxColumn Visibility="{Binding Data.IsVisible,Converter={StaticResource visibilityConverter},Source={StaticResource bindingHelper}}"/>

• مقدمه

• معرفی برنامه فصل

• مدل برنامه‌ی فصل

• ViewModel برنامه فصل

• View برنامه فصل

class DotnetTips
{
....
}

class DotnetTips:System.Object
{
...
}

DotnetTips dotnettips=new DotnetTips("i am constructor");

1. اولین کاری که CLR انجام می‌دهد، محاسبه‌ی مقدار حافظه یا تعداد بایت‌های فیلدهای شیء مربوطه است و همچنین اشیایی که از آن‌ها مشتق شده است؛ مثل System.Object که همیشه وجود دارد. هر شیء‌ایی که بر روی حافظه‌ی Heap قرار می‌گیرد، به یک سری اعضای اضافه هم نیاز دارد که Type Object Pointer و Sync Block Index نامیده می‌شوند و CLR از آن‌ها برای مدیریت حافظه استفاده می‌کند. تعداد بایت‌های این اعضای اضافه هم با تعداد بایت‌های شیء مدنظر جمع می‌شوند.
2. طبق تعداد بایت‌های به دست آمده، یک مقدار از حافظه‌ی Heap دریافت می‌شود.
3. دو عضو اضافه که در بند شماره یک به آن اشاره کردیم، آماده سازی می‌شوند.
4. سازنده‌ی شیء صدا زده می‌شود. سازنده بر اساس نوع ورودی شما انتخاب می‌شود و در صورت ارجاع به سازنده‌های والد، ابتدا سازنده‌های والد صدا زده می‌شوند و بعد از اینکه همه‌ی سازنده‌ها صدا زده شدند، سازنده‌ی System.Object صدا زده می‌شود که هیچ کدی ندارد؛ ولی به هر حال عمل Return آن انجام می‌شود.

@page "/lifecycle"
@using System.Threading

<div class="border">
    <h3>Lifecycles Parent Component</h3>

    <div class="border">
        <LifecycleChild CountValue="CurrentCount"></LifecycleChild>
    </div>

    <p>Current count: @CurrentCount</p>

    <button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
    <br /><br />
    <button class="btn btn-primary" @onclick=StartCountdown>Start Countdown</button> @MaxCount
</div>

@code
{
    int CurrentCount = 0;
    int MaxCount = 5;

    private void IncrementCount()
    {
        CurrentCount++;
        Console.WriteLine("Parnet - IncrementCount is called");
    }

    protected override void OnInitialized()
    {
        Console.WriteLine("Parnet - OnInitialized is called");
    }

    protected override async Task OnInitializedAsync()
    {
        await Task.Delay(100);
        Console.WriteLine("Parnet - OnInitializedAsync is called");
    }

    protected override void OnParametersSet()
    {
        Console.WriteLine("Parnet - OnParameterSet is called");
    }

    protected override async Task OnParametersSetAsync()
    {
        await Task.Delay(100);
        Console.WriteLine("Parnet - OnParametersSetAsync is called");
    }

    protected override void OnAfterRender(bool firstRender)
    {
        if (firstRender)
        {
            Console.WriteLine("Parnet - OnAfterRender(firstRender == true) is called");
            CurrentCount = 111;
        }
        else
        {
            CurrentCount = 999;
            Console.WriteLine("Parnet - OnAfterRender(firstRender == false) is called");
        }
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        await Task.Delay(100);
        Console.WriteLine("Parnet - OnAfterRenderAsync is called");
    }

    protected override bool ShouldRender()
    {
        Console.WriteLine("Parnet - ShouldRender is called");
        return true;
    }

    void StartCountdown()
    {
        Console.WriteLine("Parnet - StartCountdown()");
        var timer = new Timer(TimeCallBack, null, 1000, 1000);
    }

    void TimeCallBack(object state)
    {
        if (MaxCount > 0)
        {
            MaxCount--;
            Console.WriteLine("Parnet - InvokeAsync(StateHasChanged)");
            InvokeAsync(StateHasChanged);
        }
    }
}

<h3 class="ml-3 mr-3">Lifecycles Child Componenet</h3>

@code
{
    [Parameter]
    public int CountValue { get; set; }

    protected override void OnInitialized()
    {
        Console.WriteLine("  Child - OnInitialized is called");
    }

    protected override async Task OnInitializedAsync()
    {
        await Task.Delay(100);
        Console.WriteLine("  Child - OnInitializedAsync is called");
    }

    protected override void OnParametersSet()
    {
        Console.WriteLine("  Child - OnParameterSet is called");
    }

    protected override async Task OnParametersSetAsync()
    {
        await Task.Delay(100);
        Console.WriteLine("  Child - OnParametersSetAsync is called");
    }

    protected override void OnAfterRender(bool firstRender)
    {
        if (firstRender)
        {
            Console.WriteLine("  Child - OnAfterRender(firstRender == true) is called");
        }
        else
        {
            Console.WriteLine("  Child - OnAfterRender(firstRender == false) is called");
        }
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        await Task.Delay(100);
        Console.WriteLine("  Child - OnAfterRenderAsync is called");
    }

    protected override bool ShouldRender()
    {
        Console.WriteLine("  Child - ShouldRender is called");
        return true;
    }
}

<li class="nav-item px-3">
    <NavLink class="nav-link" href="lifecycle">
        <span class="oi oi-list-rich" aria-hidden="true"></span> Lifecycles
    </NavLink>
</li>

@code
{
    protected override void OnInitialized()
    {
        Console.WriteLine("Parnet - OnInitialized is called");
    }

    protected override async Task OnInitializedAsync()
    {
        await Task.Delay(100);
        Console.WriteLine("Parnet - OnInitializedAsync is called");
    }

<LifecycleChild CountValue="CurrentCount"></LifecycleChild>

Parnet - IncrementCount is called
Parnet - ShouldRender is called
  Child - OnParameterSet is called
  Child - ShouldRender is called
Parnet - OnAfterRender(firstRender == false) is called
  Child - OnAfterRender(firstRender == false) is called
  Child - OnParametersSetAsync is called
  Child - ShouldRender is called
  Child - OnAfterRender(firstRender == false) is called
  Child - OnAfterRenderAsync is called
Parnet - OnAfterRenderAsync is called
  Child - OnAfterRenderAsync is called

@code
{
    protected override void OnAfterRender(bool firstRender)
    {
        if (firstRender)
        {
            Console.WriteLine("Parnet - OnAfterRender(firstRender == true) is called");
            CurrentCount = 111;
        }
        else
        {
            CurrentCount = 999;
            Console.WriteLine("Parnet - OnAfterRender(firstRender == false) is called");
        }
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        await Task.Delay(100);
        Console.WriteLine("Parnet - OnAfterRenderAsync is called");
    }
}

@page "/lifecycle"
@using System.Threading

button class="btn btn-primary" @onclick=StartCountdown>Start Countdown</button> @MaxCount

@code
{
    int MaxCount = 5;

    void StartCountdown()
    {
        Console.WriteLine("Parnet - StartCountdown()");
        var timer = new Timer(TimeCallBack, null, 1000, 1000);
    }

    void TimeCallBack(object state)
    {
        if (MaxCount > 0)
        {
            MaxCount--;
            Console.WriteLine("Parnet - InvokeAsync(StateHasChanged)");
            InvokeAsync(StateHasChanged);
        }
    }
}

<button @onclick="OnClick">Synchronous</button>
<button @onclick="OnClickAsync">Asynchronous</button>
@code{
    void OnClick()
    {
    } // StateHasChanged is called after the method

    async Task OnClickAsync()
    {
        text = "click1";
        // StateHasChanged is called here as the synchronous part of the method ends

        await Task.Delay(1000);
        await Task.Delay(2000);
        text = "click2";
    } // StateHasChanged is called after the method
}

public partial class FrmBase<T> : Form where T : class 
    {
        public FrmBase()
        {
            InitializeComponent();
        }
    }

partial class FrmBase<T> where T : class 
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose( bool disposing )
        {
            if ( disposing && ( components != null ) )
            {
                components.Dispose();
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(186, 22);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(51, 13);
            this.label1.TabIndex = 0;
            this.label1.Text = "فرم اصلی";
            // 
            // FrmBase
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(445, 262);
            this.Controls.Add(this.label1);
            this.Name = "FrmBase";
            this.Text = "Form1";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
    }

public partial class FrmTest : FrmBase<String>
    {
        public FrmTest()
        {
            InitializeComponent();
        }
    }

    public partial class FrmTest : FrmTestHelp
    {
        public FrmTest()
        {
            InitializeComponent();
        }
    }

    public class FrmTestHelp : FrmBase<String>
    {
    }

@page "/demoHotel"

        <div class="col-12">
            <h4 class="text-info">Hotel Rooms</h4>
            <span>Rooms Selected - @SelectedRooms</span>
        </div>
        @foreach (var room in Rooms)
        {
            <IndividualRoom Room="room"></IndividualRoom>
        }

@code{

    int SelectedRooms;

    void RoomSelectionCounterChanged(bool isRoomSelected)
    {
        if (isRoomSelected)
        {
            SelectedRooms++;
        }
        else
        {
            SelectedRooms--;
        }
    }
    // ...
}

<input type="checkbox" @onchange="RoomCheckBoxSelectionChanged" />

@code
{
    //...

    [Parameter]
    public EventCallback<bool> OnRoomCheckBoxSelection { get; set; }

    async Task RoomCheckBoxSelectionChanged(ChangeEventArgs e)
    {
        await OnRoomCheckBoxSelection.InvokeAsync((bool)e.Value);
    }
}

@foreach (var room in Rooms)
{
    <IndividualRoom OnRoomCheckBoxSelection="RoomSelectionCounterChanged" Room="room"></IndividualRoom>
}

<div class="bg-light border p-2 col-5 offset-1 mt-2"
    @onclick="args => AmenitySelectionChanged(args, Amenity.Name)">
    <h4 class="text-secondary">Amenity - @Amenity.Id</h4>
    @Amenity.Name<br />
    @Amenity.Description<br />
</div>

@code
{
    [Parameter]
    public BlazorAmenity Amenity { get; set; }

    [Parameter]
    public EventCallback<string> OnAmenitySelection { get; set; }

    protected async Task AmenitySelectionChanged(MouseEventArgs e, string name)
    {
        await OnAmenitySelection.InvokeAsync(name);
    }
}

@onclick="args => AmenitySelectionChanged(args, Amenity.Name)"

@page "/demoHotel"

    @foreach (var amenity in AmenitiesList)
    {
      <IndividualAmenity OnAmenitySelection="AmenitySelectionChanged" Amenity="amenity"></IndividualAmenity>
    }

    <div class="col-12">
        <p class="text-secondary"> Selected Amenity : @SelectedAmenity </p>
    </div>

@code{

    string SelectedAmenity = "";

    void AmenitySelectionChanged(string amenity)
    {
        SelectedAmenity = amenity;
    }
}