Properly Implementing the Strategy Pattern

Context.cs

using System;

/// <summary>
/// The context, which consumes a strategy.
/// </summary>
public class Context
{
    protected IStrategy Strategy { get; set; }

    public Context(IStrategy strategy)
    {
        Strategy = strategy;
    }

    public virtual void DoWork()
    {
        Strategy.DoWork();
    }
}

IStrategy.cs

using System;

/// <summary>
/// The strategy's interface.
/// <para>The Strategy pattern is a behavioral pattern, whose
/// purpose is to define a family of algorithms, encapsulate 
/// each one, and make them interchangeable. Strategy lets 
/// the algorithm vary independently from clients that use 
/// it.</para>
/// </summary>
public interface IStrategy
{
    void DoWork();
}

StrategyA.cs

using System;

/// <summary>
/// Concrete strategy A
/// </summary>
public class StrategyA : IStrategy
{
    public virtual void DoWork()
    {
        // Do work this way.
    }
}

StrategyB.cs

using System;

/// <summary>
/// Concrete strategy B
/// </summary>
public class StrategyB : IStrategy
{
    public virtual void DoWork()
    {
        // Do work that way.
    }
}