Expression Tree Tutorial TypeIs Expression
You can build an expression tree which checks if an object is compatible with a given type using Expression.TypeIs method. For example, you have the following code.
Employee e = new Employee(); object objEmp = e as object; if(objEmp is Employee) { Console.WriteLine("It is an Empoyee object"); } else { Console.WriteLine("It is not an Empoyee object"); }
Here is the code that is required to build the same functionality using expression tree.
TypeBinaryExpression testCondition = Expression.TypeIs(
Expression.Constant(objEmp),
typeof(Employee));
var ifTrueBlock = WriteLineExpression("It is an Empoyee object");
var ifFalseBlock = WriteLineExpression("It is not an Empoyee object");
var ifThenExpr = Expression.IfThenElse(testCondition, ifTrueBlock, ifFalseBlock);
Expression.Lambda<Action>(ifThenExpr).Compile()();