C# 4 and .NET 4

752 ❘ ChaPTer 28 mAnAGed extensibility frAmewOrk
}
}
}
foreach (var item in operations)
{
Console.WriteLine("Name: {0}, number operands: {1}", item.Name,
item.NumberOperands);
operationsDict.Add(item.Name, item);
}
Console.WriteLine();
string selectedOp = null;
do
{
try
{
Console.Write("Operation ");
selectedOp = Console.ReadLine();
if (selectedOp.ToLower() == "exit" ||
!operationsDict.ContainsKey(selectedOp))
continue;
var operation = operationsDict[selectedOp];
double[] operands = new double[operation.NumberOperands];
for (int i = 0; i < operation.NumberOperands; i++)
{
Console.Write("\t operand {0} ", i + 1);
string selectedOperand = Console.ReadLine();
operands[i] = double.Parse(selectedOperand);
}
Console.WriteLine("calling calculator");
double result = Calculator.Operate(operation, operands);
Console.WriteLine("result: {0}", result);
}
catch (FormatException ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine();
continue;
}
} while (selectedOp != "exit");
The output of one sample run of the application is shown here:
Name: +, number operands: 2
Name: -, number operands: 2
Name: /, number operands: 2
Name: *, number operands: 2
Operation +
operand 1 3
operand 2 5
calling calculator
result: 8
Operation -
operand 1 7
operand 2 2
calling calculator
result: 5
Operation exit
Without recompiling the host application, it is possible to use a completely different add-in library. The
assembly AdvCalculator defines a different implementation for the Calculator class to offer more
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