I am trying to create a delegate(as a test) for: Public Overridable ReadOnly Property PropertyName()As String My intuitive attempt was declaring the delegate like this:
[code]...
So the question is, how do I make a delegate for a property?
I'm building an abstract class that handles some common operations for all of my data access objects. The class will utilize generics, so I can't make direct calls to constructors, business object properties, etc. Reflection is way too slow for what I want to accomplish, so I am using a DynamicMethod, ILGenerator, and Delegate caching instead (sample will follow).
The method I'm currently working on is a Private Shared method that populates a list of business objects using records from a data table. I'm having a problem building the property setter via IL. I'm getting an object reference error, but I'm not sure how to fix it. I believe the error comes from the "target" being Nothing, but the parameter I'm passing as the target is not Nothing at the time of invocation. Here are some snippets of what I've got so far:
'class declaration -- TList is strongly-typed list of T
Public MustInherit Class DataAccessBase(Of T, TList)
...
'delegate declaration
[code]...
I'm assuming the obj is not being passed correctly as the target, thus causing the target to be Nothing.
This code snippet was converted from the c# snippet on this link A ChildWindow management service for MVVM applications There are two classes in this snippet first is my confirmessage class
[Code]...
Now this works fine in C# , however in vb,net the line where I add the event handler generates the following error on the message.callback property : Property access must assign to the property or use its value I am tearing out my hair on this I have never used the Action of T delegate before so could i be missing something simeple ? I can provide the c# code as well.
This is a theoretical question, I've already got a solution to my problem that took me down a different path, but I think the question is still potentially interesting.Can I pass object properties as delegates in the same way I can with methods? For instance:
Let's say I've got a data reader loaded up with data, and each field's value needs to be passed into properties of differing types having been checked for DBNull. If attempting to get a single field, I might write something like:
if(!rdr["field1"].Equals(DBNull.Value)) myClass.Property1 = rdr["field1"];
But if I've got say 100 fields, that becomes unwieldy very quickly. There's a couple of ways that a call to do this might look nice:
myClass.Property = GetDefaultOrValue<string>(rdr["field1"]); //Which incidentally is the route I took
Which might also look nice as an extension method:
myClass.Property = rdr["field1"].GetDefaultOrValue<string>();
Or:
SetPropertyFromDbValue<string>(myClass.Property1, rdr["field1"]); //Which is the one that I'm interested in on this theoretical level
In the second instance, the property would need to be passed as a delegate in order to set it.
from the documentation we have this: Multicast Delegate: Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
so am i right to say that Multicast delegate is no different from a normal delegate other than the fact that it has arguments. so System.Action is a 'normal' delegate whereas System.Action(T)(Byval obj as T) is a multicast delegate?
I've created a Delegate that I intend to call Async.
[Code]...
Code:
Public Class SendPings
Shared Sub New()
AddHandler Post.Saved, AddressOf Post_Saved[code].....
I get a error" Method 'Private Shared Sub Ping(item As BlogEngine.Core.IPublishable, itemUrl As System.Uri)' does not have a signature compatible with delegate 'Delegate Sub WaitCallback(state As Object)'.
I have a function Process(data, f) where data is a normal parameter and f is a function needed to process the data (passed as a delegate to Process)
The signature of f is int f(a,b,c), with a, b, c supplied by Process when it calls the delegate.
Up until here, standard delegate usage.
Now, I have a special but common case where I would like to call Process with a constant f function. So I would like to write SimpleProcess(data, k) so that the caller does not need to create a delegate in this case, just pass the constant k (the only information needed).
So I need to dynamically create a constant function, g(a,b,c) which takes 3 parameters (which are ignored) and always returns k. This has to be done within the SimpleProcess function, so that I can then simply call Process(data, g) from within that function, without the need to rewrite the whole Process function for this special case.
Is there a way to create a delegate instance in .Net using CodeDom? I want to generate something which looks like the following:Dim myDelegate As someDelegateType = New someDelegateType(AddressOf implementingMethod)Below is more info on the context...Original Question:I am using CodeDom from the .Net framework (v3.5 if it matters) to generate a class. One of the classes defines a delegate method which in VB.Net looks like:Public Delegate Function filterByIdDelegate(ByVal obj As Object, ByVal id As Integer) As BooleanI then have a method which will provide the implementation:Private Function filterById(ByVal obj As Object, ByVal id As Integer) As Boolean Return (obj.ID = id)nd FunctionHere's the problem; how do you create an instance of the delegate (using the equivalent of AddressOf for VB.Net)? I am currently doing this (<filterByIdFunctionName> is a string holding the name of the delegate function, `' is the name of the delegate field):
Dim getFunction = New System.CodeDom.CodeMemberMethod()
With getFunction
'Declare delegate instance
[code].....
For a class, I have to create a delegate and use the function in my program called DoStuff(). There is an error tht says "Method 'Public Sub DoStuff(stringVal As String)' does not have a signature compatible with delegate 'Delegate Sub MyDel()'.
[Code]...
I have a code below to make collection that bind to a gridview able to sort by clicking on the column header. The problem here is "IPerson" is unknown at compile time. I want the delegate type able to decide by getting from gridview datasource.[code]....
View 1 RepliesI am trying to create a property which is as a class, which contains other certant properties you can edit, i.e:
Public Class exampleClass
Dim _var1 As String
Dim _var2 As Integer
[Code]....
I am trying to write a VB.NET alternative to a C# anonymous function.I wish to call Threading.SynchronizationContext.Current.Send which expects a delegate of type Threading.SendOrPostCallback to be passed to it. The background is here, but because I wish to both pass in a string to MessageBox.Show and also capture the DialogResult I need to define another delegate within. I am struggling with the VB.NET syntax, both from the traditional delegate style, and lambda functions.My go at the traditional syntax is below, but I have gut feeling it should be much simpler than this:
Private Sub CollectMesssageBoxResultFromUserAsDelegate(ByVal messageToShow As String, ByRef wasCanceled As Boolean)
wasCanceled = False
[code].....
I'd like to do something like this:
Private _myCollection As IList(Of T)
Public Property MyProperty(Of T)() as IList(Of T)
Get
[Code]....
Basically, I want to have a collection of items that may be of any type. Then, I'll be able to do something like this:
Dim myPropertyValue as <the type of some value>
if (MyProperty.Contains(<some value>))
myPropertyValue = CType(MyProperty(<some value>), <the type of some value>)
How can I do this? Or is there a better way than using a generic type?
I am trying to create a property for objects, though I am not sure if that is what it is called. For example, PictureBox.Image instead of Image I want to use my own property.
View 3 RepliesI want to create a property handler in .NET. I have already implemented the IInitializeWithFile, IPropertyStore and IPropertyStoreCapabilities classes but I don't know how to implement their functions to create custom properties and display data.[url]...
View 1 RepliesWhen you create a property in a VB.NET class how do you tell it which category it will belong to when it shows up in the property window?
View 4 RepliesI have class called "Employee" and I have a class called Department. They have an association. I need to create a colleciton of employees with the creation of a Departmant. I know how to do with using "private" member _AllMyEmployees. But I need to expose this private member using properties. therefore how do i covert thsi private member to a property? [code]
View 2 RepliesHow to create a property like combobox?
View 6 RepliesMy final goal is to have a property contain 2 values, the first value will be used the normal way you would in a property,
Eg.
myClass.myProperty = "myName"
dim str as String = myClass.myProperty
and the second value, will be metaData,
[Code]....
I have created a new user control (ctlMyBox) with a bunch of labels, textboxes, and a picturebox. I learned how to add simple custom properties (strings, integers..etc) to it using the "Public Property..etc" method.
However, as an example, I also want to add a "Theme" property with only three options (Light, Dark, and Colorful). Depending on the theme chosen for the control, the colors of the different labels will change.My current (primitive) solution to this is making the Theme property as a String, like so:
Code:
Private strTheme As String = "Colorful"
Public Property Theme() As String
Get
[code].....
This would require the user to know the exact names of the available themes. What I want is that when someone is coding to change the theme, a list of options would appear after writing ctlMyBox1.Theme = . The user would then select one of the three options, similar to when you select the checked state property of a checkbox for example. Unfortunately I don't know how to do this?
I have created a little demo application which is able to create a meeting request by using the Exchange WebService (EWS). I would also like to add some custom properties to this item but up to now I have only found examples which use the Exchange Managed API, which I won't use. There must be a way to create these properties by only using EWS... Does anybody know how and can provide a little code example?
View 1 RepliesI was wondering how I could create a property for DataGridView Items. I'd like each one to have a property called "Flooded" for this game I'm making (I thought it would be funny to make a game outside of an actual game engine). Can I declare a property or anything?
View 13 RepliesI've recently taken over a MVVM project started by someone who's now left the company; It's my first time using WPF, but by the looks of it, it was his first time using both WPF and OOP...Anyway, I've got a ListView in the XAML, and I've got a collection class which doesn't currently contain a "SelectedItem" property.what code I need to put in to link the SelectedItem of the ListView to the as-yet-unwritten SelectedItem property of my collection, and then what code I need to put in so that the SelectedItem of the collection links back to the ListView?
View 2 RepliesI am currently learning VB.net but for a project I need to create and array and pass it using a property. The data to be passed will be a train's destination, the time its due and the expected time of the train. I was wondering if someone could simplly explain how to first produce an array and then show how to pass it to a custom control
View 1 RepliesI'm having some trouble with a class that uses the ToolStripControlHost, I have to create a label and a label beside the textbox, this works, the problem now and I can not access the property. Text of textbox (txt). the class to this:
Public Class ToolStripTextBoxWithLabel
Inherits ToolStripControlHost
Public Event TextoAlterado(ByVal sender As System.Object, ByVal e As System.EventArgs)[code]......
defauld the usercontrol create(when is used) the backgroundimage property, but these property can be blocked? i'm asking these, because i need the entire control in that property
View 11 RepliesIs there a (simple) way to connect a textbox, label etc. to a property in a class?I have a project with a complex series of dialogs to enter data into a list of a costum class describing an experiment with many parameters that are stored as properties (both simple variables such as strings and integers, but also more complex ones).I need both to be able to update the list of my experiment class, but also to go the other way to populate the dialogs from the class.It can of course be done outside the class and the dialogs in separate subroutines. This however, quicly becomes unmanagable and hard to maintain as the dialogs and experiment class is expanded with new elements.If there was a simple way to connect say a textbox or label in a dialog with the appropriate property holding the information it would make it much easier.
View 5 RepliesI`m looking for a way to parse a parameter name like linq does.I want to filter before i download the date from the database.With LINQ the data is already red into a dataset. I only want to select data from the database witch i need. how i can send a property name to a function without using the property name as string and without to use to mutch code inside the function and without creating an instance of the object, etc.
Module
Module1
Dim user
As user =
[code]....
how to create my own custom property that is an object but that allows a string to be passed in to the property grid to configure it.For example, with a font type property you can type "Microsoft Sans Serif, 18pt" into the property grid and it will create the appropriate font structure and fill it.
View 5 Replies