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Sharing New up dgn Expression Tree di .NET Windows Store (Win8 app) RRS feed

  • Diskusi Umum

  • Rekans,

    just sharing pas bikin mini-MVVM framework in-house

    http://geeks.netindonesia.net/blogs/zeddy/archive/2012/11/19/new-up-using-expression-tree-in-windows-8-net-windows-store.aspx

    Ternyata Expression Tree di .NET for Windows Store masih se-powerful .NET Desktop, berikut compiled lambda untuk kode var x = new Object()  

    *lebih cepat dibanding .NET Reflection Activator.CreateInstance

    #region new Object() using Expression Tree!

    #region Delegates

    public delegate BaseViewModel InstanceCreator(params object[] args);

    #endregion

    public static InstanceCreator GetCreator(ConstructorInfo cInfo)

    {

        Type type = cInfo.DeclaringType;

        ParameterInfo[] paramsInfo = cInfo.GetParameters();

        // parameter of type object[] named args

        ParameterExpression paramExpr = Expression.Parameter(typeof (object[]), "args");

        var argsExpr = new Expression[paramsInfo.Length];

        // get each arg from object[] args

        // and create SomeType arg expression

        // eg. (int parameterA)

        for (int i = 0; i < paramsInfo.Length; ++i)

        {

            ConstantExpression index = Expression.Constant(i);

            Type argType = paramsInfo[i].ParameterType;

            BinaryExpression accessprExpr = Expression.ArrayIndex(paramExpr, index);

            UnaryExpression castExpr = Expression.Convert(accessprExpr, argType);

            argsExpr[i] = castExpr;

        }

        // new Constructor(param1, param2, ...)

        NewExpression newExpr = Expression.New(cInfo, argsExpr);

        // create lambda in order to compile expression

        LambdaExpression lambda = Expression.Lambda(typeof (InstanceCreator), newExpr, paramExpr);

        var compiledLambda = (InstanceCreator) lambda.Compile();

        return compiledLambda;

    }

    #endregion

    Sharing oleh: Zeddy Iskandar


    Best Regards,
    Agnes Sannie [MSFT]
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    Kamis, 29 November 2012 08.00
    Moderator

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