WPF Instantiate And Add User Controls By Type String?
Jul 7, 2008
I have a WPF windows project with a base Window, and then a series of user controls which I want to add at runtime based on a string from a file. I'm reading a string say "controlA" and i want to create an instance of the user control with the class name "controlA" and then add it to a base window. I want to have a constructor, but for now I would just like to see it work without.I need to do this: read a string (which is the user control type), create an instance of a user control based on that string, and then add the instance to the current WPF window. I've been playing around with Reflection.Assembly, getType, System.Activator.createInstance, Invokemember, CreateObject, and a few others. I can't seem to get it to work.
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Sep 3, 2011
System.String is a class type, but why we can use it without instantiate it with New keyword?
For example:
Dim CommandLineParameters As String = Microsoft.VisualBasic.Interaction.Command
No new keyword being used at all?
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May 15, 2012
I have a requirement where I need to have a "type safe" way of accessing property names, without actually instantiating an object to get to the property. To give an example, consider a method that takes as arguments a list of IMyObject and a string that represents a property name (a property that exists in IMyObject).
The methods implementation will take the list and access all the objects in the list using the property name passed... for some reason or another, we won't dwell on that!!
Now, I know that you can do this using an instantiated object, something like ...
Dim x as MyObject = nothing
Dim prop As PropertyInfo = PropHelper.GetProperty(Of MyObject)(Function() x.MyProperty)
Where my helper method uses reflection to get the name of the property as a string - there are numerous examples of this flying around on the web!
But I don't want to have to create this pointless object, I just want to do something like MyObject.MyProperty! Reflection allows you to iterate through a types properties and methods without declaring an object of that type... but I want to access a specific property and retrieve the string version of its name without iteration and without declaring an object of that type!
The main point here is that although I am trying to get the property name as a string... this is done at run time... at compile time, I want this to be type safe so if someone changes the property name, the compilation will break.
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Jul 22, 2010
Following is my code. Private Structure DISPLAY_ELEMENT_TYPE
[Code]...
Actually this is vb6 to .net converted code. I m getting compile error at following line
temp = Lset(DispElem(i)) bcz Lset is not supported in .Net Lset accept string data type for first parameter and interger for second.If you know any alternet solution or if you have any source code for Explicit convert UDT to string type and vice versa.
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Oct 31, 2009
i wanted to do something simple that sort of replicate an object:
public function clone(byval realcopy as object) as object return new Control ' something like this works, however i want to return the type of realcopy, which may not be a control end function so i tried this:
public function clone(byval realcopy as object) as object
return new gettype(realcopy.gettype)
end function
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Feb 6, 2012
I am attempting to write a programme where a user can type in a 'string' into a textbox. A data dictionary will contain specific keywords relating to a specific classification, where an algorithm can detect whether any of the keywords occur in the 'string'. Here are the processes that need to occur:
1) A data dictionary, that contains keywords relating to specific classes eg. (IT Issues, Printer, Software, Password).
2) An algorithm needs to compare the words in the Data Dictionary to that of the 'string' to detect any matches.
3) A rule set to determine what classification the 'string' needs to be classed as.
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Mar 12, 2010
How can I instantiate an anonymous object while passing the propertynames and values as string?
new With { .SomeProperty = "Value" }
new With { ".SomeProperty" = "Value" }
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Nov 25, 2009
Im trying to improve some apps ive written, the first is a console app... Im trying to get it so that i wont get an invalidcastexception if the user inputs a string, when the variable is type "Double"
[Code]....
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Jul 22, 2010
I have an Account Class that is able to create notes(Class), however i am able to create the note object by itself which is not the desired outcome, i want only the account class to be able to create the note object. Another Example would be, an order item should not be created without an order class. But how do you enforce this in vb.net.
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Feb 8, 2012
I am trying to write a generic method, to avoid code duplication, which will create or activate a Form as an MDI children, based on its type. But I have to lines in error (see comments).
[Code]...
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Aug 23, 2011
There is newer code in a follow up post. I suggest using the code in the later post rather than the code in this one. You can still read this post though. When designing a user interface, one should be conscious of how many individual controls are required to implement the functionality. In some cases an initial design may begin with many buttons or textboxes (for example) but then further review of
the actual required functionality allows for a reduction in the number of unique controls.
But other times, there isn't a better way (which will still make sense to the user of the application) then to have a series of many repeated controls. So in the cases where one can be certain that the best UI implementation for an application will require the use of multiple copies of a given control, then it often becomes necessary to maintain some method of managing all of those controls at various points
throughout the application. Doing so typically requires that one build up some collection of controls which can then be accessed by index in order to work with any given control; but this can lead to a lot of clutter in the code file which handles these control's events. For instance there will be some kind of collection declaration, some recursive routine to find all of the controls of interest, and then any number of event handler methods with long lists of Handles clauses, or additional code loops to wire up the event handling for each control.
Purpose Since most of this functionality could be considered a requirement regardless of the type of control being managed, or its required functionality, it may make sense to wrap all of the control management functionality into a single class. And since our first requirement is a collection of controls, then a base collection class could be the perfect starting point for our control manager. There are a number of existing thread around this topic, with some recent (at the time of this writing) ones being:[URL]..In this, and related, threads I have posted examples of a simple TextBoxManager and ButtonManager control. But again, with so much similar functionality required regardless of the control being managed, it would be technically possible to create a generic ControlManager(Of T As Control) class which can manage any type of control.
[Code]...
So in summary, one can facilitate managing a large number of user interface controls by building a "control manager" class which both encapsulates the list of control instances, and deals with adding and removing defined event handlers for every control it manages. The generic control manager class itself can be inherited and extended into a more specific class on a per-application basis in order to provide more application-specific functionality. Reed Kimble - "When you do things right, people won't be sure you've done anything at all"
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Aug 11, 2009
dim myCollection as new Specialized.StringCollection
dim myFoundThings as new ArrayList
dim index as Integer
dim newResultMemberName as String
[code]....
This is part of some code that will run without user interaction once it's spinning away, and I need to create a unique object from some items found in a StringCollection, naming the objects using information found in the strings stored in that StringCollection.
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Sep 27, 2011
I have some custom user controls in my .net winforms program that do not display correctly when the user has selected larger text size. This setting:
My controls look like this:
Instead of like this:
The bill to area and ship to area are both custom controls. I don't know if this is contributing to the problem but I do have code in each to scale the phone/fax areas to stretch nicely, like this code from the bill to control,
Private Sub panFaxPhone_Resize(sender As Object, e As System.EventArgs) Handles panFaxPhone.Resize
panFax.Width = (panFaxPhone.Width / 2) - 1
panPhone.Width = (panFaxPhone.Width / 2) - 1
panFax.Left = panFaxPhone.Width - panFax.Width
End Sub
How can I get my controls to size correctly while still respecting the users choice for larger text (I don't want to just set the AutoScaleMode to None)? After playing with this for a long time it seems to be a problem with anchors in the child controls. See this below image, the inner black box is the control with its border turned on, the text boxes (like name) are anchored left and right and should stretch to fill the control, but don't.
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Jun 2, 2012
i have a windows from project and in that project i created a user control lets call itcustombutton1 now i can use that control quite easily either at design time or runtime by creating a new instance of it like
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Dec 21, 2009
I'm in the process of porting an old excel addin that was writen in VBA to VB .NET. The Excel addin interacts with a number of external com objects. The code sorta looks like this:[code...]
What I'm trying to do is read the string from the COM object and get it in durr for use later in my program.
That second line results in the exception posted above. If I try casting with CStr/CType I get the same exception.
The visual studio watch window reports the type of hurr.getString as a "System.__ComObject" whereas the VBA watch window reports the type as "Variant/Object/String".
Microsoft.VisualBasic.Information.TypeName(hurr.getString) says the type is "String".
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Dec 2, 2009
How many controls can I have before I should start looking at user defind controls because of too many controls making my program go slow?
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Dec 16, 2011
I am trying to make it so when I use Me.Controls("Timer1") for example I can access specific commands for a timer such as Stop() Start(), I tried CType() and typed in "Timer" as the type but it says the control type can't be converted to the "Timer" type.
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Mar 11, 2010
my code is :
[Code]...
The error is Value of type '1-dimensional array of string' cannot be converted to 'String'.
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Mar 11, 2010
I need something tje user can type in data to such a parts QTY cost etc. There are no predefined parts list so the user can enter any part name/Number and there is no limit to amount of parts that can be entered.
Does anyone have any idea what might be useful. It was thinks of a listview bu i can't see that you can type into that. I cant use comboboxs because there are no predefined list and i know there is some way to generate text at runtime (i think) but i don't know how to do it and i would prefer a clearer approach.
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Jun 11, 2009
i want to know how to type cast to user defined type in vb.net.I have a mark object which contains student id , subject name,subject id and mark. I have to read the subject id from a combo box and read corresponding mark value from it to a text box.
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Oct 17, 2009
When trying to combine the User path with another path, I get a an error:"Conversion from string "User" to type 'Integer' is not valid."
vb.net Dim Variable As String = IO.Path.Combine(Environment.GetFolderPath(Environment.UserName), _
"AppDataLocalLowSunJavaDeploymentcache") I guess my understanding of how to combine paths is a bit unclear. I didn't realize that by doing it this way, I was attempting to convert the path to an integer.
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Mar 22, 2010
I'm trying to add a new record to my database but i keep getting the message - "conversion from type DBnull to type string is not valid". I think its something to do with the Employee ID when VB attempts to save it to the database my code is below
Imports System.Data.OleDb
Public Class Add
Private Sub DisplayRow()
[Code]....
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May 25, 2011
I now have SQL Parameters set up and I'm using them to save/delete/add my data. This all works well, except when it's trying to save a combobox to the datatable it appears with the error above.Majority of my comboboxes have datasources, and the valuemembers of these are the actual list items, not the ID's of the list items.I'm not sure why this error could be happening, I'm fairly sure I've connected everything to the binding source correctly; I've checked it a few times.Does anybody know what the cause of this could be? I've looked around a bit and I haven't found much
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Apr 19, 2010
I had write code (just for learning), the codes :
dim Temp as string
Temp = Recordset("
Table_Field")
but, when I start Debugging the error messages "Unable to cast object of type 'ADODB.InternalField' to type 'System.String"
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Mar 19, 2009
I'm new to VB 2005, the code below is actualy coded from VB 6 and just converted it to VB 2005. I'm having trouble with line that's on bold letters.In VB 6 this works just ok. By the way the error message is "Unable to cast object of type 'System.String' to type 'ADODB.Connection'." [code]
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May 16, 2007
I have these errors when creating my website?
Error 1Server Error in '/ Application. -------------------------------------------------------------------------------- Conversion from type 'DBNull' to type 'String' is not valid. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid. Source Error: Line 64:
Line 65:
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Jun 15, 2009
how can I solve this error without having to fill all of my fields. Some of the fields in my database are Nulls and some have records.
Error: Conversion from type 'DBNull' to type 'String' is not valid.
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Jan 27, 2012
I am getting this error No mapping exists from object type System.String[] to a known managed provider native type.The code is
Dim conn1 As SqlConnection
conn1 = New SqlConnection("Data Source=win2008-2;Initial Catalog=h1tm11;User ID=sa;Password=#1cub3123*;Persist Security Info=True;")
' Dim conn1 As String = ConfigurationManager _ .ConnectionStrings("Connectionstring").ConnectionString()
'conn1.ConnectionString = ConfigurationManager.ConnectionStrings("Data Source=win2008-2;Initial Catalog=h1tm11;User ID=sa;
[code].....
the error occurs at adapter.Fill(table)
Dim addressstring1 As String = txtpostcode.Value.Trim()
Dim addressstring() As String = Split("addressstring1", ",", 1)
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May 2, 2010
I am getting the error "Conversion from type 'DataGridViewTextBoxCell' to type 'String' is not valid." When trying to display a cell from DGV in a listbox.I have my variable for the cell reference as follows:
Dim a As Object
a = DataGridView1(4,1)
To insert it in the listbox as follows:
lstLetter.Items.Add(String.Format(a))
I tried:
lstLetter.Items.Add(a)
This will not actually display the entry inside the referenced cell, it shows this in my listbox instead:
DataGridView TextBoxCell { ColumnIndex=4, RowIndex=1 }
how I need to convert this to display.
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Jul 29, 2011
I was tried to get quantity from db make use of the selection in list box. I got answered with listbox1. If i selected the item in listbox1 the quantity would appear in textbox1. But in this same code will not work for listbox2 with textbox4.. Here i given the code...
$Con.open()
$Dim cd as new oledb.oledbcommand("Select Quantity from tlist where tool_name"& "'"listbox2.selecteditem & "'" & "", con)
[Code]....
Here i got the error as "Conversion from type DBNull to type string is not valid"
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