.NET API Documentation

Example

This example demonstrates how to throw an InvalidOperationException when an operation cannot be performed because the object is not in the correct state.

// Imagine a state machine where a transition is attempted in an invalid state.
public class StateMachine
{
    private enum State { Idle, Running, Stopped }
    private State currentState = State.Idle;

    public void Start()
    {
        if (currentState != State.Idle)
        {
            throw new InvalidOperationException("Cannot start. Machine is not in Idle state.");
        }
        currentState = State.Running;
        Console.WriteLine("Machine started.");
    }

    public void Stop()
    {
        if (currentState != State.Running)
        {
            throw new InvalidOperationException("Cannot stop. Machine is not in Running state.");
        }
        currentState = State.Stopped;
        Console.WriteLine("Machine stopped.");
    }

    public void Process()
    {
        if (currentState != State.Running)
        {
            throw new InvalidOperationException("Cannot process. Machine is not in Running state.");
        }
        Console.WriteLine("Processing data...");
    }
}

// Usage
try
{
    StateMachine sm = new StateMachine();
    sm.Start();
    sm.Process();
    sm.Start(); // This will throw an exception
}
catch (InvalidOperationException ex)
{
    Console.WriteLine($"Error: {ex.Message}");
}