IUserDataContainer

IUserDataContainer is an interface for classes that can hold user-data.

/// <summary>Interface for classes that can hold user-data.</summary>
public interface IUserDataContainer
{
    /// <summary>Is <see cref="UserData"/> assigned.</summary>
    bool HasUserData { get; }

    /// <summary>Policy whether this implementation constructs <see cref="UserData"/> lazily.</summary>
    bool UserDataInitializedOnGet { get; }

    /// <summary>User-data in concurrent safe map. Lazy constructed on get. If object set to read-only state, so is <see cref="UserData"/> map.</summary>
    /// <remarks>Setter use is discouraged. The implementation is allowed to prevent it by throwing <see cref="InvalidOperationException"/>.</remarks>
    /// <exception cref="InvalidOperationException">If modifying read-only object, or if class prohibits setting data object.</exception>
    IDictionary<string, object?> UserData { get; set; }
}

UserDataContainerBase can be used as base class. This base class requires explicit dictionary assignment to .UserData.

public class MyClass0 : UserDataContainerBase { }

IUserDataContainer container = new MyClass0();
container.UserData = new ConcurrentDictionary<string, object?>();
container.UserData["Hello"] = "World";
WriteLine(container.UserData["Hello"]); // "World"

UserDataContainerBase.LazyConstructed is base class that lazy-initializes .UserData on getter.

public class MyClass1 : UserDataContainerBase.LazyConstructed { }

IUserDataContainer container = new MyClass1();
container.UserData["Hello"] = "World";
WriteLine(container.UserData["Hello"]); // "World"

.SetUserData(key, value) is an extension method that assigns a value to .UserData.

IUserDataContainer container = new MyClass1().SetUserData("Hello", "World");
WriteLine(container.UserData["Hello"]); // "World"

ReadOnlyAssignableClass.UserDataContainerLazyConstructed is base class that implements both IReadOnly and IUserDataContainer.

public class MyClass2 : ReadOnlyAssignableClass.UserDataContainerLazyConstructed { }

IUserDataContainer container = new MyClass2().SetUserData("Hello", "World").SetReadOnly();
WriteLine(container.UserData["Hello"]); // "World"

Dictionary is set to read-only state along with container.

try
{
    IUserDataContainer container = new MyClass2().SetReadOnly().SetUserData("Hello", "World");
} catch (InvalidOperationException e)
{
    WriteLine(e);
}

Full Example

Full example

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using Avalanche.Message;
using Avalanche.Utilities;
using static System.Console;

class userdatacontainer
{
    public static void Run()
    {
        {
            // <00>
            IUserDataContainer container = new MyClass0();
            container.UserData = new ConcurrentDictionary<string, object?>();
            container.UserData["Hello"] = "World";
            WriteLine(container.UserData["Hello"]); // "World"
            // </00>
        }
        {
            // <01>
            IUserDataContainer container = new MyClass1();
            container.UserData["Hello"] = "World";
            WriteLine(container.UserData["Hello"]); // "World"
            // </01>
        }
        {
            // <02>
            IUserDataContainer container = new MyClass1().SetUserData("Hello", "World");
            WriteLine(container.UserData["Hello"]); // "World"
            // </02>
        }

        {
            // <03>
            IUserDataContainer container = new MyClass2().SetUserData("Hello", "World").SetReadOnly();
            WriteLine(container.UserData["Hello"]); // "World"
            // </03>
        }
        {
            // <04>
            MyClass2 container = new MyClass2();
            IDictionary<string, object?> data = container.UserData;
            container.SetReadOnly();
            try
            {
                data["Hello"] = "World";
            } catch (InvalidOperationException e)
            {
                WriteLine(e);
            }
            // </04>
        }
        {
            // <05>
            try
            {
                IUserDataContainer container = new MyClass2().SetReadOnly().SetUserData("Hello", "World");
            } catch (InvalidOperationException e)
            {
                WriteLine(e);
            }
            // </05>
        }
    }

    // <100>
    public class MyClass0 : UserDataContainerBase { }
    // </100>
    // <101>
    public class MyClass1 : UserDataContainerBase.LazyConstructed { }
    // </101>
    // <102>
    public class MyClass2 : ReadOnlyAssignableClass.UserDataContainerLazyConstructed { }
    // </102>
}