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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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  • How to find the first declaring method for a reference method

    - by Oliver Gierke
    Suppose you have a generic interface and an implementation: public interface MyInterface<T> { void foo(T param); } public class MyImplementation<T> implements MyInterface<T> { void foo(T param) { } } These two types are frework types. In the next step I want allow users to extend that interface as well as redeclare foo(T param) to maybe equip it with further annotations. public interface MyExtendedInterface extends MyInterface<Bar> { @Override void foo(Bar param); // Further declared methods } I create an AOP proxy for the extended interface and intercept especially the calls to furtherly declared methods. As foo(…) is no redeclared in MyExtendedInterface I cannot execute it by simply invoking MethodInvocation.proceed() as the instance of MyImplementation only implements MyInterface.foo(…) and not MyExtendedInterface.foo(…). So is there a way to get access to the method that declared a method initially? Regarding this example is there a way to find out that foo(Bar param) was declared in MyInterface originally and get access to the accoriding Method instance? I already tried to scan base class methods to match by name and parameter types but that doesn't work out as generics pop in and MyImplementation.getMethod("foo", Bar.class) obviously throws a NoSuchMethodException. I already know that MyExtendedInterface types MyInterface to Bar. So If I could create some kind of "typed view" on MyImplementation my math algorithm could work out actually.

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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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  • 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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  • 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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  • Custom Attributes on Class Members

    - by ccook
    I am using a Custom Attribute to define how a class's members are mapped to properties for posting as a form post (Payment Gateway). I have the custom attribute working just fine, and am able to get the attribute by "name", but would like to get the attribute by the member itself. For example: getFieldName("name"); vs getFieldName(obj.Name); The plan is to write a method to serialize the class with members into a postable string. Here's the test code I have at this point, where ret is a string and PropertyMapping is the custom attribute: foreach (MemberInfo i in (typeof(CustomClass)).GetMember("Name")) { foreach (object at in i.GetCustomAttributes(true)) { PropertyMapping map = at as PropertyMapping; if (map != null) { ret += map.FieldName; } } } Thanks in advance!

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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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  • 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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  • 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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  • 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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  • 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 To Test if a Type is Anonymous?

    - by DaveDev
    Hi Guys I have the following method which serialises an object to a HTML tag. I only want to do this though if the type isn't Anonymous. private void MergeTypeDataToTag(object typeData) { if (typeData != null) { Type elementType = typeData.GetType(); if (/* elementType != AnonymousType */) { _tag.Attributes.Add("class", elementType.Name); } // do some more stuff } } Can somebody show me how to achieve this? Thanks Dave

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  • The uncatchable exception, pt 2

    - by chaiguy
    Ok I've done some testing and I've reduced the problem to something very simple: i. Create a method in a new class that throws an exception: public class Class1 { public void CallMe() { string blah = null; blah.ToLower(); } } ii. Create a MethodInfo that points to this method somewhere else: Type class1 = typeof( Class1 ); Class1 obj = new Class1(); MethodInfo method = class1.GetMethod( "CallMe" ); iii. Wrap a call to Invoke() in a try/catch block: try { method.Invoke( obj, null ); // exception is not being caught! } catch { } iv. Run the program without the debugger (works fine). v. Now run the program with the debugger. The debugger will halt the program when the exception occurs, even though it's wrapped in a catch handler that tries to ignore it. (Even if you put a breakpoint in the catch block it will halt before it reaches it!) In fact, the exception is happening when you run it without the debugger too. In a simple test project it's getting ignored at some other level, but if your app has any kind of global exception handling, it will get triggered there as well. This is causing me a real headache because it keeps triggering my app's crash-handler, not to mention the pain it is to attempt to debug.

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  • Dynamic Method Creation

    - by TJMonk15
    So, I have been trying to research this all morning, and have had no luck. I am trying to find a way to dynamically create a method/delegate/lambda that returns a new instance of a certain class (not known until runtime) that inherits from a certain base class. I can guarantee the following about the unknown/dynamic class It will always inherit from one known Class (Row) It will have atleast 2 constructors (one accepting a long, and one accepting an IDataRecord) I plan on doign the following: Finding all classes that have a certain attribute on them Creating a delegate/method/lambda/whatever that creates a new instance of the class Storing the delegate/whatever along with some properties in a struct/class Insert the struct into a hashtable When needed, pull the info out of the hashtable and calling the delegate/whatever to get a new instance of the class and returning it/adding it to a list/etc. I need help only with #2 above!!! I have no idea where to start. I really just need some reference material to get me started, or some keywords to throw into google. This is for a compact/simple to use ORM for our office here. I understand the above is not simple, but once working, should make maintaining the code incredibly simple. Please let me know if you need any more info! And thanks in advance! :)

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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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  • 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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  • 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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  • f# types' properties in inconsistent order and of slightly differing types

    - by philbrowndotcom
    I'm trying to iterate through an array of objects and recursively print out each objects properties. Here is my object model: type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedTradeRecommendations = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; } Here is how I am instantiating my objects: let getMyIdeasIdeas = [| {id=1; ticker="msfqt"; direction="buy"; author={authorId=0; authorName="john Smith"; firm={firmId=12; firmName="Firm1"}};}; {id=2; ticker="goog"; direction="sell"; author={authorId=1; authorName="Bill Jones"; firm={firmId=13; firmName="ABC Financial"}};}; {id=3; ticker="DFHF"; direction="buy"; author={authorId=2; authorName="Ron James"; firm={firmId=2; firmName="DEFFirm"}};}|] And here is my algorithm to iterate, recurse and print: let rec recurseObj (sb : StringBuilder) o= let props : PropertyInfo [] = o.GetType().GetProperties() sb.Append( o.GetType().ToString()) |> ignore for x in props do let getMethod = x.GetGetMethod() let value = getMethod.Invoke(o, Array.empty) ignore <| match value with | :? float | :? int | :? string | :? bool as f -> sb.Append(x.Name + ": " + f.ToString() + "," ) |> ignore | _ -> recurseObj sb value for x in getMyIdeas do recurseObj sb x sb.Append("\r\n") |> ignore If you couldnt tell, I'm trying to create a csv file and am printing out the types for debugging purposes. The problem is, the first element comes through in the order you'd expect, but all subsequent elements come through with a slightly different (and confusing) ordering of the "child" properties like so: RpcMethods+denormalizedSuggestedTradeRecommendationsid: 1,ticker: msfqt,direction: buy,RpcMethods+authorIdentifierauthorId: 0,authorName: john Smith,RpcMethods+firmIdentifierfirmId: 12,firmName: Firm1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 2,ticker: goog,direction: sell,RpcMethods+authorIdentifierauthorName: Bill Jones,RpcMethods+firmIdentifierfirmName: ABC Financial,firmId: 13,authorId: 1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 3,ticker: DFHF,direction: buy,RpcMethods+authorIdentifierauthorName: Ron James,RpcMethods+firmIdentifierfirmName: DEFFirm,firmId: 2,authorId: 2, Any idea what is going on here?

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  • How to determine if a .NET Type is a custom struct?

    - by SztupY
    Hi! How to write a simple method, that checks whether a concrete type is a custom struct (created with public struct { };) or not. Checking Type.IsValueType is not enough, because it is also true to int, long, etc, and adding a check to !IsPrimitiveType won't exclude decimal, DateTime and maybe some other value types. I know that most of the built in value types are actually "structs", but I only want to check for "custom structs" These questions are mostly the same but without the answer I need: #1 #2 #3

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