TryCatchExpression Example

C# Code : 

Action<int, int> trySample = (a, b) =>
                {
                    try
                    {
                        int result = a / b;
                        Console.WriteLine("Result : {0}", result);
                    }
                    catch (System.DivideByZeroException)
                    {
                        Console.WriteLine("cannot divide by zero");
                    }
                    catch (Exception)
                    {
                        Console.WriteLine("UnexpectedException");
                        throw;
                    }
                    finally
                    {
                        Console.WriteLine("bloc finally");
                    }
                };

Expression Trees Code :

var aParam = Expression.Parameter(typeof(int), "a");
var bParam = Expression.Parameter(typeof(int), "b");
var resultVariable = Expression.Variable(typeof(int), "result");

Expression<Action<int, int>> expression =
    Expression.Lambda<Action<int, int>>(
        //{
        Expression.Block(
                new[] { resultVariable },
                Expression.TryCatchFinally(
                               //try
                                Expression.Block(
                               //int result = a / b;
                               Expression.Assign(resultVariable, Expression.Divide(aParam, bParam)),
                               //Console.WriteLine("Result : {0}", result);
                               Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(int) }), resultVariable)),
                 // finally {Console.WriteLine("bloc finally"); }
                Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }),
                 Expression.Constant("bloc finally")),
                //catch (System.DivideByZeroException)
                Expression.Catch(typeof(DivideByZeroException),
                                // Console.WriteLine("cannot divide by zero");
                               Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }),
                                Expression.Constant("cannot divide by zero"))),
                //catch (Exception)
                Expression.Catch(typeof(Expression),
                               //{
                               Expression.Block(
                               //Console.WriteLine("UnexpectedException");
                               Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] {                                typeof(string) }),
                               Expression.Constant("UnexpectedException")),
                                //throw;
                               Expression.Rethrow())))),
     aParam, bParam);

Expression Trees Debug View : 

.Lambda #Lambda1<System.Action`2[System.Int32,System.Int32]>(
    System.Int32 $a,
    System.Int32 $b) {
    .Block(System.Int32 $result) {
        .Try {
            .Block() {
                $result = $a / $b;
                .Call System.Console.WriteLine($result)
            }
        } .Catch (System.DivideByZeroException) {
            .Call System.Console.WriteLine("cannot divide by zero")
        } .Catch (System.Linq.Expressions.Expression) {
            .Block() {
                .Call System.Console.WriteLine("UnexpectedException");
                .Rethrow
            }
        } .Finally {
            .Call System.Console.WriteLine("bloc finally")
        }
    }
}

IL Code : 

//int result = a / b;
IL_0000: ldarg.1
IL_0001: ldarg.2
IL_0002: div
IL_0003: stloc.0
//Console.WriteLine("Result : {0}", result);
IL_0004: ldloc.0
IL_0005: call 6000003 System.Console.WriteLine(Int32)
IL_000a: leave IL_0031
IL_000f: pop
IL_0010: ldstr 70000005 "cannot divide by zero"
IL_0015: call 6000006 System.Console.WriteLine(System.String)
IL_001a: leave IL_0031
IL_001f: pop
//Console.WriteLine("UnexpectedException");
IL_0020: ldstr 70000008 "UnexpectedException"
IL_0025: call 6000009 System.Console.WriteLine(System.String)
//throw;
IL_002a: rethrow
IL_002c: leave IL_0031
IL_0031: leave IL_0041
//Console.WriteLine("bloc finally");
IL_0036: ldstr 7000000a "bloc finally"
IL_003b: call 600000b System.Console.WriteLine(System.String)
IL_0040: endfinally
IL_0041: ret