Expression Tree Tutorial Switch Expression
The Expression.Switch creates a SwitchExpression that represents a switch statement that has a default case.
- All SwitchCase objects in a SwitchExpression object must have the same type unless the SwitchExpression has the type void.
- Each SwitchCase object has an implicit break statement, which means that there is no implicit fall through from one case label to another.
- If switchValue does not match any of the cases, the default case represented by default body is run.
For example, you have the following code.
int value = 4; switch (value) { case 1: Console.WriteLine("First Case"); break; case 2: Console.WriteLine("Second Case"); break; case 3: Console.WriteLine("Third Case"); break; default: Console.WriteLine("Default Case"); break; }
Here is the code that is required to build the same functionality using expression tree.
ConstantExpression switchValue = Expression.Constant(4); var defaultCase = WriteLineExpression("Default Case"); var case1 = WriteLineExpression("First Case"); var case2 = WriteLineExpression("Second Case"); var case3 = WriteLineExpression("Third Case"); // This expression represents a switch statement // that has a default case. SwitchExpression switchExpr = Expression.Switch( switchValue, defaultCase, new SwitchCase[] { Expression.SwitchCase(case1,Expression.Constant(1)), Expression.SwitchCase(case2,Expression.Constant(2)), Expression.SwitchCase(case3,Expression.Constant(3)) } ); Expression.Lambda<Action>(switchExpr).Compile()();