/* We can use the MultiplyToAdd class to modify the expression created in previous example
* and create a new method that doubles any parameter given to it. */
private static void ModifyingAnExpressionTreeExample()
{
//build the expression tree: Expression<Func<int,int>> square = num => num * num;
//The parameter for the expression is an integer
ParameterExpression numParam = Expression.Parameter(typeof(int), "num");
//The operation to be performed is to square the parameter
BinaryExpression squareOperation = Expression.Multiply(numParam, numParam);
//This creates an expression tree that describes the square operation
Expression <Func <int, int> > square = Expression.Lambda <Func <int, int> >(
squareOperation,
new ParameterExpression[] { numParam });
//Compile the tree to make an executable method and assign it to a delegate
Func <int, int> doSquare = square.Compile();
//Call the delegate
Console.WriteLine("Square of 2: {0}", doSquare(2));
//Modify the expression to replace the multiply with an add
MultiplyToAdd m = new MultiplyToAdd();
Expression <Func <int, int> > addExpression = (Expression <Func <int, int> >)m.Modify(square);
Func <int, int> doAdd = addExpression.Compile();
Console.WriteLine("Double of 4: {0}", doAdd(4));
}
public static void exectuteTest()
{
ParameterExpression numParam = Expression.Parameter(typeof(int), "num");
BinaryExpression squareOption = Expression.Multiply(numParam, numParam);
Expression <Func <int, int> > square = Expression.Lambda <Func <int, int> >(squareOption, new ParameterExpression[] { numParam });
Func <int, int> doSquare = square.Compile();
Console.WriteLine($"Result square {doSquare(2)}");
Console.WriteLine();
Console.ReadKey();
MultiplyToAdd m = new MultiplyToAdd();
Expression <Func <int, int> > addExpression = (Expression <Func <int, int> >)m.Modify(square);
Func <int, int> doAdd = addExpression.Compile();
Console.WriteLine($"Result add {doAdd(4)}");
Console.WriteLine();
Console.ReadKey();
}
// An expression tree is immutable, which means that the elements in the expression cannot be changed once the expression
// has been created. To modify an expression tree you must make a copy of the tree which contains the modified
// behaviors.
public void ModifyingExpressionTree()
{
Expression <Func <int, int> > squareExp = num => num * num;
MultiplyToAdd m = new MultiplyToAdd();
Expression <Func <int, int> > addExpression = (Expression <Func <int, int> >)m.Modify(squareExp);
Func <int, int> doAdd = addExpression.Compile();
Console.WriteLine("Double of 4: {0}", doAdd(4));
}
