C# - How To See If A Type Implements An Interface
Oct 25, 2010
I need to know if a Type implements an interface. [Code] because the Interface IRule itself is assignable of IRule what raises a MissingMethodExcpetion if i try to create an instance:
ruleObj = CType(Activator.CreateInstance(typeAsm, True), Rule.IRule)
UPDATE2: IsAssignableFrom in combination with IsAbstract might be the best way to check if a given type implements an interface and is not the interface itself (what throws a MissingMethodException if you try to create an instance).
If GetType(Rule.IRule).IsAssignableFrom(typeAsm) AndAlso Not typeAsm.IsAbstract Then
View 5 Replies
ADVERTISEMENT
Jun 23, 2012
I had a look through the documentation on the Wiki, but it seems a bit thin. How do I determine if a type implements a given interface using Cecil? For my particular implementation it is important that I do not actually load the type into the AppDomain.m Here's the code that I have so far:
Dim outputModule As ModuleDefinition = ModuleDefinition.ReadModule(outputFile)
For Each assemblyType As TypeDefinition In outputModule.Types
'How to determine if assemblyType implements a specific interface?
View 1 Replies
Dec 4, 2009
I've got a web user control (.ascx) which implements a couple of interfaces I wrote; namely IXMLBoundControl and ISectionOverridingControl.I've written a mini-CMS type application that dynamically loads controls onto the page based on information in a database. When I click a button on a web page (.aspx), I want to look at all the controls on that page, and determine if there is a control which implements the ISectionOverridingControl.
I've got my loop and I'm looping through the controls; that's fine. However I'm not sure what the best way is to determine whether or not the control implements the interface. What I'm doing at the moment (and works) is to try to cast each control into the ISectionOverridingControl and catching InvalidCastException: If I don't get the catch; I consider it's worked. If the exception is thrown then it doesn't implement the interface.
It's working, however, I consider this inefficient (relying on exceptions): surely there's a better way in VB.NET (I've seen an example in C# but it didn't convert to VB) to tell whether an instance of a class implements an interface or not?
View 3 Replies
Sep 1, 2009
I have an object parameter and I need to check if the object implements a specified interface in vb.net. How to test this?
View 2 Replies
Sep 2, 2010
I have an interface, for the sake of argument called MyInterface.I Have a Control Class, lets name it "Parent" that implements MyInterface.I have another Control Class that inherits Parent, called "Child".I have a final Control Class lets call it "Container", that accepts dragging the parent onto it.[code]I want to modify this not to only accept Parent, but to accept ANYthing that implements MyInterface. I can't figure out how the heck to get it to work. Even more confusing, if I drag the child onto Container, with the code as it is above(checking to see if a Parent was dropped), GetDataPresent always returns false. I would figure it would work, since Child inherited parent.[code]But it bombs and GetDataPresent returns false whether I dragged a Parent or a Child. I'm being an idiot somewhere..
View 1 Replies
Jun 5, 2011
I use the IsAssignableFrom-method to check if the datasource of a bindingsource-object implements an interface i defined. The check happens inside the property-setter like this:
Private WithEvents _BindingSource As BindingSource
''' <summary>
''' BindingSource containing datasource in which search is executed.
''' </summary>
''' <remarks>Datasource must implement ISearchAndFindable.</remarks>
<Description("The BindingSource to search within."), Category("Data")> _
Public Property BindingSource() As BindingSource
[Code] .....
View 4 Replies
Nov 29, 2011
I'm not sure that I'm doing the right thing here..I'm writing a user control that's supposed to be (fairly) generic. It's a bit like a modified email client specifically tailored to some of the internal things we do.
The view is composed of two main pieces, a message list and a viewer. I need this viewer to be interchangeable, so if someone wants a different style of view they can simply handle an event and change a property. My original idea was to just have an INoteViewer, but since I'm adding it to my form I also need to guarantee that this object is a Windows.Forms.Control of some sort.
Should I continue along these lines and maybe raise an ArgumentException if I can't cast it to INoteViewer, or should I go a different direction and create a class that inherits from Windows.Forms.Control?
View 2 Replies
Sep 24, 2009
I am trying to check if a type implements the generic Icollection interface, since this is a base interface for any of my generic collections.the below code doesnt work
GetType(ICollection(Of)).IsAssignableFrom(
objValue.GetType().GetGenericTypeDefinition())
whats a good way of detecting if a type implements a generic interface?
View 2 Replies
Apr 9, 2010
I am trying to create a class in VB.NET which inherits a base abstract class and also implements an interface. The interface declares a string property called Description. The base class contains a string property called Description. The main class inherits the base class and implements the interface. The existence of the Description property in the base class fulfills the interface requirements. This works fine in C# but causes issues in VB.NET.
[Code]...
View 5 Replies
Jun 1, 2012
I am building a software which will be used to create a remote desktop connection. However I'm getting this error:
Unable to cast COM object of type 'System.__ComObject' to interface type 'MSTSCLib.IMsTscNonScriptable'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{C1E6743A-41C1-4A74-832A-0DD06C1C7A0E}' failed
due to the following error: Δεν υποστηρίζεται τέτοια διασύνδεση (Exception from HRESULT: 0x80004002 E_NOINTERFACE)).
[Code]...
View 1 Replies
Feb 14, 2012
In trying to add a bit of usage variety to a generic class I'm working on, I ran into this issue with trying to cast an object into an interface instance where the interface is defined inside the generic class.
[Code]...
View 1 Replies
May 10, 2009
I have been trying to use vb2008 to automatically update CustomDocumentProperties fields that I have set up within a pro-forma document. I can load the Word application and word document without problems.I want to update the CustomDocumentProperties fields with data read from a dB. To do this I am assuming that I need to iterate through the CustomDocumentProperties fields within the word document and when one is "found" that matches the data I wish to merge then assign the dB value to the field.The problem is that I am getting an exception error when I try to reference the document customdocumentproperties
"Error : Unable to cast the COM object of type 'System._ComObject' to interface type 'Microsoft.Office.Interop.Word.CustomProperties'. ...... "
my code looks like;
Dim WordApp As Word._Application
Dim odoc As Word._Document
Dim BContinue As Boolean = True
[code].....
View 2 Replies
May 19, 2009
I am working in VB.net and have a Class, Foo, that implements an interface, IBar.I have a List of Foo's, but I need to pass a list of IBar's into a function, but I keep getting casting errors, even when I use DirectCast.My code is [code]MainWorks works, but it would be really annoying and inefficient to have to do that everywhere I want to call this function.
View 4 Replies
Jan 6, 2012
I am trying to implement the Strategy design pattern using interfaces.However, while developing some code I stumbled upon something strange.The type of the object is not verified in design-time.Observe the following code.Notice that Foo implements IFoo and Bar DOES NOT implement this interface.No error is shown when trying this:[code]This code compiles fine. No error is shown in Visual Studio.However, when I run this piece of code, I receive an InvalidCastException.The output of the console:[code]
View 1 Replies
Jan 13, 2011
While learning to use LINQ in VB.NET, I came across the following:Dim x As IEnumerable = (some LINQ query)
If you can't instantiate an interface, but only a concrete implementation of it, why is this allowed? Is there some difference between doing Dim x as (Type) and Dim x as New (Type)?
View 1 Replies
May 20, 2009
I am working on a project that has several different codes. These codes all basically are used this way:
CodeKey
Description
GetList
GetSpecific
SetProperties
All of my classes implement this. I am hesitent, however, to use an interface because of one problem--the type Codes vary by type. Some are strings, some are integers, some are bytes. The only way I could see using an interface would be to make the typeCode an object in the interface and then cast whenever I needed to use it, but that seems a bit silly. Any ideas? This is in VB.NET.
View 1 Replies
Nov 22, 2011
I am looking to implement the ability to compare and sort classes in my model. All of the objects in my model will need some common functionality regarding to comparisons so I created an abstract BaseComparer that implements IComparer.
Public MustInherit Class BaseComparer(Of T)
Implements IComparer(Of T)
End Class
[code].....
View 2 Replies
Feb 12, 2009
I would like to check if a property's type is an interface (not a specific interface, but any interface).
dim __PropertyInfo As PropertyInfo
dim b as boolean = isinterface(__PropertyInfo)
[code].....
View 3 Replies
Mar 1, 2010
I'm currently trying to create a class that is a composition of the SqlDataAdapter class (as unfortunately you can't inherit from it). In order to try and make it as similar as possible I'm using all the same inherits and interfaces as is documented on MSDN.The problem that I am having is that there are some properties where the interface specifies that the type of the property is IDbCommand. But in the SqlDataAdapter the property type is SqlCommand.
View 3 Replies
Oct 19, 2010
what is the difference between declaring a variable in this way
ByVal
List As IEnumerable as
a parametre in a function
Dim
[Code]....
View 1 Replies
Dec 27, 2010
I would like to have a command prompt type interface on my form. The only thing I am aware of is a textbox, but there are no facilities to have commands and output scroll without keeping the entire history in a variable. That would be an ever increasing variable, which is ridiculous. Is there an alternate way to use a textbox as a command prompt, or is there something else I can do. Another note, is the use of an array. I know I can increase an array with commands, but this is no good either, because some responses in the box need to be paragraphs in length, so even a separate array for command and output is too cumbersome.
View 6 Replies
Jun 8, 2009
I have a following code which works fine
MsgBox(AddSomething(Of String)("Hello", "World"))
Public Function AddSomething(Of T)(ByVal FirstValue As T, ByVal SecondValue As T) As String
Return FirstValue.ToString + SecondValue.ToString
[code].....
View 3 Replies
Mar 1, 2011
In many projects I work on, whenever I have to return a read only collection, I use the IEnumerable<T> interface and make it type specific like so:
CODE:
Most of the time, I return a List but in some functions and read only properties I return an array which also serves the purpose alright by kind courtesy of Extension Methods.
My question is am I violating any design principles by returning IEnumerable<T>s instead of specific types (e.g.: List<T>, HashSet<T>, Stack<T> or Arrays)?
View 8 Replies
Feb 28, 2011
I am creating an xlsx reader / writer for my application (based on OpenXML SDK 2.0). I want to read xlsx files and store the data contained in each row in a DTO/PONO. Further I want to read the xlsx file and then modify it and save it.Now my problem is not with the OpenXML SDK, I can do what I need to do.My problem is on how to structure my components. Specifically I have problems with the polymorphism at the lowest level of a Spreadsheet, the cell.A cell in Excel/OpenXML can have different types of data associated with it. Like a Time, Date, Number, Text or Formula. These different type need to be handled differently when read/written from/to a spreadsheet.I decided to have a common interface for all subtypes like TextCell, NumberCell, DateCell etc.Now when I read the cell from the spreadsheet the Method/Factory can decide which type of cell to create.
Now because the cell is an abstract from the real implementation it does not know / does not need to know of what type it is. For writing / modifying the cell I solve this problem by calling .write(ICellWriter) on the cell I want to persist. As the cell itself knows what type of data it contains, it knows which method of ICellWriter it needs to call (static polymorpism).Writing to the xlsx file is no problem. My problem is, how do I get the data out of my cell into my DTO/PONO without resorting to type checking -> If TypeOf variable is ClassX then doesomething End If. As Methods / Properties have to have different Signatures and differentiating by only using a different return type is not allowed.The holder (collection, in this case a row of a table/spreadsheet) of the objects (refering to the cells) does not know the concrete implementations. So for writing a cell I pass it a Cellwriter. This Cellwriter has overloaded methods like Write(num as Integer), Write(text as String), Write(datum as Date). The cell object that gets this passed to it then calls the Write() method with the data type it holds. This works, as no return value is passed back.After some thinking about the problem I came to realize that it's not possible without reflection or knowledge of what type of cell I am expecting. Basically I was trying to recreate a spreadsheet or something with similar functionality and way too abstract/configurable for my needs.
View 1 Replies
Mar 3, 2009
Attempting to invoke a method of an interface, of which the return type is _variant_t
Code:
_variant_t resultsDataString;
_bstr_t simObjectNames;
simObjectNames = SysAllocString (L"TEST example 3");
resultsDataString = pis8->GetSimObject (simObjectNames);
[code].....
View 4 Replies
Jan 6, 2011
I have an interface ITest with a method GetResult(). I have a class Test which implements ITest and thereby defines private method GetResult().
Next I create an instance of Test in a different class. The code is as below:
Module NewClass
Public Sub New()
Dim i As ITest = New Test()
[Code]....
I am migrating existing code from VB 6 to VB.NET and hence I'm not supposed to change the access modifier of GetResult. Leaving it Private will throw InvalidCastException Unable to cast object of type 'System.Object' to type 'ITest'
Object type variable o is used in many places and hence I don't want to change that. And yes, Test implements ITest.GetMember with a different name.
View 3 Replies
Jul 9, 2009
Here is the IDL definition
[code]...
I am getting the following error:Unable to cast COM object of type 'TESTSERVERLib.TestClass' to interface type 'TESTSERVERLib.ITest'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{DAFB7D76-0158-452F-8FD0-FF97A683DEA3}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).Object reference not set to an instance of an object.Whereas the same code works from an VB .Net Forms application.Can anyone explain why this code does'nt work in a VB .NET windows service.
View 5 Replies
Mar 15, 2011
I have 2 classes that Implement 1 EventHandler. Its part of a fingerprint scanner API but I'm having some issue and I'm not sure if it is my fault in how i use the Implements.Is it ok to have 2 different classes Implement the same EventHandler? Each class then uses the events differently within the class but it almost seems like there is some overlap that is causing some issues. I know this is hard to explain without posting code but since i can pinpoint the problem, idk what to post. My main point is, can you have 2 different classes Implement the same Interface?
View 1 Replies
Dec 6, 2010
Im trying to make a program that implements this but I cant seem to get past inserting the characters. Basicly to get a better idea on what im trying to do look here.Public Function permutation(ByRef charSet As String, ByVal minInt As Integer, ByVal maxInt As Integer)
[Code]...
View 2 Replies
May 24, 2012
I have about 1000 webrequest created. Each link will navigate to a website and download a picture to place into a picturebox.
The person will then type in what animal is in the picture into a textbox. Then the user will then hit the submit button to send the name of the animal back to the site.
I am going to implement the use of a thread pool to handle the threading portion of those requests.
What is the best method to get my webrequest into the thread pool (listbox, txt file,etc?) and then how can I setup my button to coordniate with the site that is coming out of the pool to the picture box?
My first thought is to create everything on the fly. The picturebox, the textbox, and the submit button, the webrequest to the site for the picture and back again for the result. Something tells me that I will be taking the long way around to get same result.
My second thought is to have a slew of pictureboxes, textboxes, and buttons already on my screen and then when they come out of the pool and into a thread they would assigned a picturebox, textbox, and button if the others are not busy.
View 4 Replies
