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  • Nullables? Detecting them

    - by Aren B
    Ok, im still a bit new to using nullable types. I'm writing a reflecting object walker for a project of mine, im getting to the point where im setting the value of a reflected property with the value i've retrieved from a reflected property. The value i've retrieved is still in object form, and it dawned on me, since i want my object walker to return null when it can't find something, (I thought about throwing an exception, but i want this to soft-fail when something's wrong). Anyway, some of the values im setting/getting are decimal bool etc... so it dawned on me that i should just NOT set a non-nullable value, but I realized I straight up don't know how to tell decimal from decimal? Is it enough to key on if the Type of the property im setting is inherited from ValueType?

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  • Problems finding classes in namespace

    - by Matt
    I am trying to find all of the types in the Models namespace within an ASP.NET MVC assembly from within a testing assembly. I was trying to use LINQ to find the relevant set for me but it is returning an empty set on me. I am sure it is some simple mistake, I am still relatively new to LINQ admittedly. var abstractViewModelType = typeof (AbstractViewModel); var baseAssembly = Assembly.GetAssembly(abstractViewModelType); var modelTypes = baseAssembly.GetTypes() .Where(assemblyType => (assemblyType.Namespace.EndsWith("Models") && assemblyType.Name != "AbstractViewModel")) .Select(assemblyType => assemblyType); foreach(var modelType in modelTypes) { //Assert some things } When I reach the foreach I receive a Null reference exception.

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  • Java.lang.reflext.Proxy returning another proxy from invocation results in ClassCastException on ass

    - by matao
    So I'm playing with geotools and I thought I'd proxy one of their data-access classes and trace how it was being used in their code. I coded up a dynamic proxy and wrapped a FeatureSource (interface) in it and off it went happily. Then I wanted to look at some of the transitive objects returned by the featureSource as well, since the main thing a FeatureSource does is return a FeatureCollection (FeatureSource is analogous to a sql DataSource and featurecollection to an sql statement). in my invocationhandler I just passed the call through to the underlying object, printing out the target class/method/args and result as I went, but for calls that returned a FeatureCollection (another interface), I wrapped that object in my proxy (the same class but a new instance, shouldn't matter should it?) and returned it. BAM! Classcast exception: java.lang.ClassCastException: $Proxy5 cannot be cast to org.geotools.feature.FeatureCollection at $Proxy4.getFeatures(Unknown Source) at MyClass.myTestMethod(MyClass.java:295) the calling code: FeatureSource<SimpleFeatureType, SimpleFeature> featureSource = ... // create the FS featureSource = (FeatureSource<SimpleFeatureType, SimpleFeature>) FeatureSourceProxy.newInstance(featureSource, features); featureSource.getBounds();// ok featureSource.getSupportedHints();// ok DefaultQuery query1 = new DefaultQuery(DefaultQuery.ALL); FeatureCollection<SimpleFeatureType, SimpleFeature> results = featureSource.getFeatures(query1); //<- explosion here the Proxy: public class FeatureSourceProxy implements java.lang.reflect.InvocationHandler { private Object target; private List<SimpleFeature> features; public static Object newInstance(Object obj, List<SimpleFeature> features) { return java.lang.reflect.Proxy.newProxyInstance( obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), new FeatureSourceProxy(obj, features) ); } private FeatureSourceProxy(Object obj, List<SimpleFeature> features) { this.target = obj; this.features = features; } public Object invoke(Object proxy, Method m, Object[] args)throws Throwable{ Object result = null; try { if("getFeatures".equals(m.getName())){ result = interceptGetFeatures(m, args); } else{ result = m.invoke(target, args); } } catch (Exception e) { throw new RuntimeException("unexpected invocation exception: " + e.getMessage(), e); } return result; } private Object interceptGetFeatures(Method m, Object[] args) throws Exception{ return newInstance(m.invoke(target, args), features); } } Is it possible to dynamically return proxies of interfaces from a proxied interface or am I doing something wrong? cheers!

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  • Retrieving the type of a Collection

    - by nevets1219
    So I have something like the following in Java: private List<SomeType>variable; // ....variable is instantiated as so ... variable = new ArrayList<SomeType>(); // there's also a getter public List<SomeType> getVariable() { /* code */ } What I would like to be able to do is figure out that variable is a collection of SomeType programmatically. I read here that I can determine that from the method getVariable() but is there any way to tell directly from variable? I have been able to retrieve SomeType from the getter method based on the information in the link. I have also been successful in retrieving all the fields of the surrounding class via SurroundingClass.getClass().getDeclaredFields() but this doesn't tell me that it is List<SomeType>.

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  • How to allow users to customize a DAL

    - by rsteckly
    Hi, I'm working in ASP.NET in an application where often users want to add fields or change field names. I'd like to be able to have an xml schema in place that is parsed and a dynamic object model created from it that can be accessed throughout the application. My initial reaction is that this is not realistic. I think there is flexibility about the dynamic nature of it. I think the people I'm trying to build this for wouldn't mind recompiling. Even if the app recompiled, I don't know how to abstract away enough in my code access the data to allow for users changing property names, etc. How can you write LINQ when the properties might change? In short, there's two questions here: 1) is there a way to dynamically generate an object model of the database and 2) is there a way to abstract away enough so that code accessing the database doesn't break when properties change?

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  • How does AssemblyName.ReferenceMatchesDefinition work?

    - by Fabian Schmied
    Given the following code: var n1 = new AssemblyName ("TestDll, Version=1.0.0.0, Culture=Neutral, PublicKeyToken=b77a5c561934e089"); var n2 = new AssemblyName ("TestDll, Version=2.0.0.2001, Culture=en-US, PublicKeyToken=ab7a5c561934e089"); Console.WriteLine (AssemblyName.ReferenceMatchesDefinition (n1, n2)); Console.WriteLine (AssemblyName.ReferenceMatchesDefinition (n2, n1)); Why do both of these checks print "True"? I would have thought that AssemblyName.ReferenceMatchesDefinition should consider differences in the version, culture, and public key token attributes of an assembly name, shouldn't they? If not, what does ReferenceMatchesDefinition do that a comparison of the simple names doesn't?

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  • If I specify a System property multiple times when invoking JVM which value is used?

    - by RobV
    If I specify a system property multiple times when invoking the JVM which value will I actually get when I retrieve the property? e.g. java -Dprop=A -Dprop=B -jar my.jar What will be the result when I call System.getProperty("prop");? The Java documentation on this does not really tell me anything useful on this front. In my non-scientific testing on a couple of machines running different JVMs it seems like the last value is the one returned (which is actually the behavior I need) but I wondered if this behavior is actually defined officially anywhere or can it vary between JVMs?

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  • How can I find out if two arguments are instances of the same, but unknown class?

    - by Ingmar
    Let us say we have a method which accepts two arguments o1 and o2 of type Object and returns a boolean value. I want this method to return true only when the arguments are instances of the same class, e.g.: foo(new Integer(4),new Integer(5)); Should return true, however: foo(new SomeClass(), new SubtypeSomeClass()); should return false and also: foo(new Integer(3),"zoo"); should return false. I believe one way is to compare the fully qualified class names: public boolean foo(Object o1, Object o2){ Class<? extends Object> c1 = o1.getClass(); Class<? extends Object> c2 = o2.getClass(); if(c1.getName().equals(c2.getName()){ return true;} return false; } An alternative conditional statement would be : if (c1.isAssignableFrom(c2) && c2.isAssignableFrom(c1)){ return true; } The latter alternative is rather slow. Are there other alternatives to this problem?

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  • ASP.NET MVC security: how to check if a controller method is allowed to execute under current user's

    - by Gart
    Given an ASP.NET MVC Controller class declaration: public class ItemController : Controller { public ActionResult Index() { // ... } public ActionResult Details() { // ... } [Authorize(Roles="Admin, Editor")] public ActionResult Edit() { // ... } [Authorized(Roles="Admin")] public ActionResult Delete() { // .. } } I need to reflect a list of methods in this class which may be invoked with the current user's permissions. Please share some ideas of what could be done in this case.

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  • PropertyInfo from Delegate

    - by Paul Hatcherian
    Is there a simple way to get the PropertyInfo for a property in a delegate, assuming it is a simple property seletor? Example: var propertyInfo = Method<MyClass,int>(s => s.Property); ... PropertyInfo Method(Func<T1,T2> selector) { // What goes here? }

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  • Attribute lost with yield

    - by Nelson
    Here's an interesting one... There is some code that I'm trying to convert from IList to IEnumerable: [Something(123)] public IEnumerable<Foo> GetAllFoos() { SetupSomething(); DataReader dr = RunSomething(); while (dr.Read()) { yield return Factory.Create(dr); } } The problem is, SetupSomething() comes from the base class and uses: Attribute.GetCustomAttribute(new StackTrace().GetFrame(1).GetMethod(), typeof(Something)) Yield ends up creating MoveNext(), MoveNext() calls SetupSomething(), and MoveNext() does not have the [Something(123)] attribute. I can't change the base class, so it appears I am forced to stay with IList or implement IEnumerable manually (and add the attribute to MoveNext()). Is there any other way to make yield work in this scenario?

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  • listing the functions of a web service

    - by Jankhana
    hi, I wanted to make an application that will take either the path of the dll or Webservice and list me all the functions present in that dll. I accomplished the listing of the function using this but I am not able to list the functions of the Webservices. Using Assembly.GetMembers() it's listing the Function Name with the Parameters Type and I am not able to get the Parameters Name. How shall i get that? While debugging I found that m_parameters is a nonpublic member and i'm not able to get the Parameter name. Is that possible??? And one more question is how shall i list the functions available in the web service without including the web reference or service reference in the windows application using C#.

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  • Comparing Nested object properties using C#

    - by Kumar
    I have a method which compares two objects and returns a list of all the property names which are different. public static IList<string> GetDifferingProperties(object source, object) { var sourceType = source.GetType(); var sourceProperties = sourceType.GetProperties(); var targetType = target.GetType(); var targetProperties = targetType.GetProperties(); var properties = (from s in sourceProperties from t in targetProperties where s.Name == t.Name && s.PropertyType == t.PropertyType && s.GetValue(source,null) != t.GetValue(target,null) select s.Name).ToList(); return properties; } For example if I have two classes as follows: public class Address { public string AddressLine1 { get; set; } public string AddressLine2 { get; set; } public string City { get; set; } public string State { get; set; } public string Zip { get; set; } } public class Employee { public string FirstName { get; set; } public string MiddleName { get; set; } public string LastName { get; set; } public Address EmployeeAddress { get; set; } } I am trying to compare the following two employee instances: var emp1Address = new Address(); emp1Address.AddressLine1 = "Microsoft Corporation"; emp1Address.AddressLine2 = "One Microsoft Way"; emp1Address.City = "Redmond"; emp1Address.State = "WA"; emp1Address.Zip = "98052-6399"; var emp1 = new Employee(); emp1.FirstName = "Bill"; emp1.LastName = "Gates"; emp1.EmployeeAddress = emp1Address; var emp2Address = new Address(); emp2Address.AddressLine1 = "Gates Foundation"; emp2Address.AddressLine2 = "One Microsoft Way"; emp2Address.City = "Redmond"; emp2Address.State = "WA"; emp2Address.Zip = "98052-6399"; var emp2 = new Employee(); emp2.FirstName = "Melinda"; emp2.LastName = "Gates"; emp2.EmployeeAddress = emp2Address; So when I pass these two employee objects to my GetDifferingProperties method currently it returns FirstName and EmployeeAddress, but it does not tell me which exact property (which in this case is Address1) in the EmployeeAddress has changed. How can I tweak this method to get something like EmployeeAddress.Address1?

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  • Constructor invocation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • Use string value to create new instance

    - by Brian David Berman
    I have a few classes: SomeClass1, SomeClass2. How can I create a new instance of one of these classes by using the class name from a string? Normally, I would do: var someClass1 = new SomeClass1(); How can I create this instance from the following: var className = "SomeClass1"; I am assuming I should use Type.GetType() or something but I can't figure it out. Thanks.

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  • Type patterns and generic classes in Haskell

    - by finnsson
    I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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  • Delphi getting property value of a member from ClassType

    - by Kayode Yusuf
    I am implementing a Boilerplate feature - allow users to Change descriptions of some components - like Tlabels - at run time. e.g. TFooClass = Class ( TBaseClass) Label : Tlabel; ... End; Var FooClass : TFooClass; ... At Design time, the value Label's caption property is say - 'First Name', when the application is run, there is a feature that allows the user to change the caption value to say 'Other Name'. Once this is changed, the caption for the label for the class instance of FooClass is updated immediately. The problem now is if the user for whatever reason wants to revert back to the design time value of say 'First Name' , it seems impossible. I can use the RTTIContext methods and all that but I at the end of the day, it seems to require the instance of the class for me to change the value and since this has already being changed - I seem to to have hit a brick wall getting around it. My question is this - is there a way using the old RTTI methods or the new RTTIContext stuff to the property of a class' member without instantiating the class - i.e. getting the property from the ClassType definition. This is code snippet of my attempt at doing that : c : TRttiContext; z : TRttiInstanceType; w : TRttiProperty; Aform : Tform; .... Begin ..... Aform := Tform(FooClass); for vCount := 0 to AForm.ComponentCount-1 do begin vDummyComponent := AForm.Components[vCount]; if IsPublishedProp(vDummyComponent,'Caption') then begin c := TRttiContext.Create; try z := (c.GetType(vDummyComponent.ClassInfo) as TRttiInstanceType); w := z.GetProperty('Caption'); if w <> nil then Values[vOffset, 1] := w.GetValue(vDummyComponent.ClassType).AsString ..... ..... .... .... I am getting all sorts of errors and any help will be greatly appreciated.

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