sample calculator interfacing

Main.cs

void Main()
{
	var operators = new IOperator[]{
		new AdditionOperator()
		
	};
	var calc = new Calculator(operators);
	calc.InputNumber("1");
	calc.Operator = operators[0];
	calc.ApplyOperator().Dump();

}

// Define other methods and classes here

public interface IOperator
{
	string Name { get; }
	string Display { get; }
	int Apply(int x, int y);
}

public interface ICalculator
{
	IOperator Operator { get; set; }
	// store the input for applying operators
	void InputNumber(string value);
	IEnumerable<IOperator> Operations { get; }
	// there may not be two numbers input yet
	int? ApplyOperator();
	string Display { get; }

}

// sample operator
public class AdditionOperator : IOperator
{
	public int Apply(int x, int y) => x + y;
	public string Name => "Addition";
	public string Display => "+";
}

public class Calculator : ICalculator
{
	int val1 = 0;
	int val2 = 0;
	// this could solve the val2 never getting set problem
	public IOperator Operator { get; set; }
	public IEnumerable<IOperator> Operations { get; }
	public int? ApplyOperator() => this.Operator?.Apply(val1,val2);
	public void InputNumber(string value){
		int.TryParse(value,out val1);
	}
	public string Display => val1.ToString();
	public Calculator(IEnumerable<IOperator> operations) => this.Operations = operations;
}

// bonus Factory Interface
//Factory pattern

public interface IMakeCalculators{
	ICalculator Make(IEnumerable<IOperator> ops);
}