.net - Getting Base Field Type When Databinding To A Decimal (or Object) Property?
May 28, 2012
I've got a custom NumericEditor control that has a nullable Decimal property called Value. When I bind a data field to Value, I'd like to retrieve the underlying Type of the data that's bound, so that I can restrict the use of decimal places if the source field is an integral data type.I figure I'd have to do this in the BindingContextChanged event, but how do I get the Type of the data field from the binding itself? My Google-Fu is failing me at the moment.
In short, I'm looking for something like the GetValueType method mentioned in the following question: Simple databinding - How to handle bound field/property change. Winforms, .Net I imagine this method would also be handy if the Value property was an Object.
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May 28, 2012
I have written a .Net 4.0 Winforms Numeric Editor control (which inherits from TextBox), and I have added a Value property that is a nullable decimal type, as follows:
Public Class NumericEditor
Inherits TextBox
Private _value As Decimal? = Nothing
[code]....
how to get around this exception, particularly when I'm databinding a number field to a number property, and there should be no string conversion happening. (To further complicate things, I'm using a similar technique for another control where I databind a DateTime field to a nullable DateTime property, and that control works just fine.)
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Jan 15, 2010
on a Windows Form, an object myObject is bound to myObjectDataBindingSource like this:myObjectDataBindingSource .DatSource = myObject on the form, i have a check box bound to the property: chkProp1 for example of the object: myObjectDataBindingSource In the code when the checkbox is clicked, I need to go in code and change another text property of the object txtProper2 for example like this:
Private Sub chkProp1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkProp1.CheckedChanged
[code].....
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Oct 19, 2009
I have a custom control with a bindable property:-
Private _Value As Object
<Bindable(True), ... > _
Public Property Value() As Object
Get
[code]....
Also, here, I'm adding a handler to the DataBindings.CollectionChanged event.This is the second place that I retrieve the type:-
Private Sub DataBindings_CollectionChanged(ByVal sender As Object, ByVal e As System.ComponentModel.CollectionChangeEventArgs)
If e.Action = CollectionChangeAction.Add Then
Dim b As Binding = DirectCast(e.Element, Binding)
[code]....
I need the first place, because the BindingContextChanged event is not fired until some time after InitializeComponent.The second place is needed if the binding field is programatically changed.Am I handling the correct events here, or is there a cleaner way to do it?
Note: My GetValueType method uses the CurrencyManager.GetItemProperties....etc, to retrieve the type.
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Feb 7, 2012
I am pulling data from a local MSSQL database using a stored procedure, then send the data to a web service. Every part of the component works well except for a pesky problem will a DBNull being returned from the DataRow field, when I know that the field is not null and has valid data. The database and associated INSERT statements that add to this field are designed to not allow NULL entries. When I debug break the program on or right before the line that throws the error I see that the field has valid data for the current row.If I add a null check to the code (as below) the operation continues as normal:
Dim dataResultsTable = Me.myViewTableAdapter.GetData(int)
For Each myDataRow In dataResultsTable.Rows
If worker.CancellationPending Then
[code]....
Why is the read operation returning DBNull instead of the data in the database?
EDIT: Just to be clear, the operation does return the proper data, but the data is not being saved into the variable.
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Dec 7, 2011
I'm trying to create a Window with a ListView and an Area where details to the selected Object are displayed. The Listview displays items stored in an ObservableCollection(Of T) Collection. The items itself contain also an ObservableCollecton(Of T) Collection which should then be displayed in the details area in another ListView, accordingly to the selected item of the first ListView.
The Problem: The InitializeComponent() throws an Exception (XAMLParseException).
Exception:Set property 'System.Windows.Controls.GridViewColumn.DisplayMemberBinding' threw an exception.
InnerException:Object of type 'System.String' cannot be converted to type 'System.Windows.Data.BindingBase'.
The Line- and ColumNumer of the Exception are Pointing at the <GridView> of my ListView (.View).This is the First ListView
<ListView ItemsSource="{Binding Path=MyObjectCollection, Mode=OneWay}" SelectedItem="{Binding Path=Selected, Mode=OneWayToSource}">
<ListView.View>[code]....
So. How can I bind to the Collection Property of an Object could be nothing?
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Oct 8, 2010
I have a project that has mainly two objects, both inheriting from a base. Like this:
Public Class Vehicle
Property Model As String
Property Make As String[code].....
The above function doesn't work because myVehicle is a Vehicle, not a Truck.Is there a way I can pass around a Vehicle type and have the IDE know which type to use? Or am I completely missing a better way to do this?
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Apr 20, 2010
When I click on a header (Price) to sort the rows by that column, I get an error Object must be of type decimal.
I'm thinking that I'm encountering a new row without any values that's why this error is being generated.
I'm not sure how to intercept this error or fix it for that matter....
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Mar 24, 2011
[code] I get this error Name of field or property being initialized in an object initializer must start with '.' How should I write this? Or is there an alternative way of doing this?
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Nov 15, 2011
My LINQ query is as follows
Dim Query = From t In New XPQuery(Of xUser)(Xpo.Session.DefaultSession)
.Where("Name=John").Select("new (Name as FirstName)")
Unfortunately i get the error No property or field 'John' exists in type 'xUser'.Of course no such property exists in my xUser class, but hot can i fix that?After reading within the DynamicLinq Class i found this function
Function FindPropertyOrField(ByVal type As Type, ByVal memberName As String, ByVal staticAccess As Boolean) As MemberInfo
Dim flags As BindingFlags = BindingFlags.Public Or BindingFlags.DeclaredOnly Or _
If(staticAccess, BindingFlags.Static, BindingFlags.Instance)[code]...
How can i edit my "faulty" query? What am i doing wrong here?
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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 10, 2010
I am somewhat new to object oriented programming and am attempting to flatten a Linq object hierarchy by using a shim class.how to initalize a derived class with property values from a base class?I have two objects, a base object with about 100 properties, and a derived object which inherits from the base object and adds a few additional properties beyond those of the base object. My simple constructor creates the derived object, but I am looking for a way to initialize the derived object properties with values from the base object.Right now I am using reflection to iterate over the properties individually and I suspect there may be a better way. The following example shows my shim class constructor for the derived class, and two properties:
newProperty1 - a new string property of the derived class
flattenedProperty2 - a new string property of the derived class, copied from a 2nd-level object of the base class
Code example:
Public Class derivedObj
Inherits baseObj
Private _newProperty1 As String[code].......
Is this the correct constructor approach to flatten the object hierarchy using a shim class? My second question relates to initialization of properties in the derived class. The constructor above creates the derived object, but what is the best way to initialize the derived object properties with values from the base object? The following code uses reflection to iterate over the properties individually, but I suspect there may be a better way.
Code example:
' property names are in the string array fieldNames
'baseObjQuery is an ienumerable of baseObj
'derivedObjList is a list of derivedObj[code].....
Is there a simple way to initialize values for the properties in the derived object based upon the values of the common properties in the base object?
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Nov 14, 2009
In a vb .net winforms app I am trying out something for "wide and shallow" children of a record. I use strongly typed business objects ( Strataframe ).My plan is to have a number of "child tables" collected in a dataset I drop on the form. they have no correspondence in persisted data, so the dataset is untyped and I am creating the schema through the property sheet for the tables. Each table is the datasource for a datagridview in the interface.
In my proof of concept sample, My main businessobject (CustomerBO) interacts with a SQL Server 2008 table with fields - pk, name, - and a third column which is currently varchar(max) as I considered XML but could just as easily be varbinary(max) if that works better for holding the serialized dataset.
bo.bigfield will be the strongly typed prop I want to hold the byte() array or XML or whatever that represents the dataset for that record.So, the question in a nutshell - how do I convert a dataset to a single datum and reproduce the dataset from that datum. This is my first foray into datasets, datagridviews as well so if there are better ways to accomplish any of that I'm listening.
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Feb 15, 2012
I am building a code behind page that has a public property (MyDTOItem) which is essentially a DTO object (dtDTOItem) Note: In my code the Get and Set are actually real code (I stripped it for the example).The problem I am having is in the Page_Load event. When I set the .Member1 property of the DTO object the Get code runs and not the Set and therefore the DTO ibject property .Member1 never gets assigned. I figured out that if I add code (MyDTOItem = New dtDTOItem) to the Page_Load event then it will set the value correctly. What I am trying to figure out is how to initialize the property object without having to do it explicitly. It has to be an extended property because I have custom Get and Set code.
Public Property MyDTOItem As dtDTOItem
Get
End Get
Set(value As dtDTOItem)
[code]....
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Jun 5, 2006
I am building a code behind page that has a public property (MyDTOItem) which is essentially a DTO object (dtDTOItem) Note: In my code the Get and Set are actually real code (I stripped it for the example).
The problem I am having is in the Page_Load event. When I set the .Member1 property of the DTO object the Get code runs and not the Set and therefore the DTO ibject property .Member1 never gets assigned.
I figured out that if I add code (MyDTOItem = New dtDTOItem) to the Page_Load event then it will set the value correctly. What I am trying to figure out is how to initialize the property object without having to do it explicitly. It has to be an extended property because I have custom Get and Set code.
Public Property MyDTOItem As dtDTOItem
Get
End Get
[code]....
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Jul 5, 2010
bare with me during this silly example. :-) Let's say I have a class like this:
Public Class Animal
Public iLegs as int32 ' Number of legs
Public bWings as Boolean ' Wings? Yes/No
End Class
And another class that inherits the "Animal" class and adds one more property:
Public Class ScaryAnimal
Inherits Animal
Public iScariness as int32 ' 0-100, how scary is it?
End Class
Now, if I have an instance of "Animal" with some values in it, and I decide I want to cast it to a ScaryAnimal for some reason, how do I do that without having to create a new instance of "ScaryAnimal" and copy each property value?Basically I'm looking for a way to do this, without having to write the lines marked with '*** below:
[Code]...
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Feb 9, 2010
[code]......
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Jun 16, 2009
Error in VB code "Name of field or property being initialized in an object initializer must start with '.'_"
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Mar 5, 2011
sir i've one text field and two tables named table1,table2
i've to just display text from two different tables using two different navigations for each table.
1.when i'll click on first navigation, data from first table should have to display in textbox
2. when i'll click on second navigation, data from second table should have to display in same textbox alternatively
i've to show data in only one text box alternatively
i've binded designtime table1 to textbox
so how to unbind it & bind table2 to same texbox runtime.
like that i've 12 tables & 12 navigation for each table and only one text filed
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Aug 20, 2009
I have a number of controls (Device1, Device2, etc.) that all inherit from BaseDeviceControl. In the DragEnter event handler I am trying to test for the correct type by using the BaseDevvceControl like this....
[Code]....
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Apr 23, 2010
I would like to databind to a property that requires arguments.
I thought about defining custom columns and cells because the parameters that the property requires are available from the within the object bound to the row, but I'm having trouble materialising this idea.
As an additional problem, that I think leads on from this, I have also created a custom column and cell for the datagridview that takes the implementation of an interface during it's construction. I have added this column to the datagrid view programmatically (passing the Interface implementation to the column constructor). I've overridden the paint method which evaluates a property from the Interface implantation using arguments from the other rows in the column, but it doesn't seem to call the paint method at all. Even on DataGridView.Refresh(). Essentially I would like this column to also update, evaluate a property from the interface implentation using arguments from the underlying object bound to the row and print this number in the cell.
The reason for this second problem is so that I can implement the interface many different times and just at a column dynamically to display it's evaluation.
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Nov 23, 2010
In this example the IsEnabled property of my button is bound to the selected rows "Local" property of the grid and it works just fine:
<Button DockPanel.Dock="Bottom" Width="100" Height="100" IsEnabled="{Binding ElementName=dataGridRestore , Path=SelectedItem.Local}"></Button>
<my:DataGrid x:Name="dataGridRestore"
ItemsSource="{Binding}"
[Code]...
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Nov 23, 2009
I have a copy function that I'd like to override in subclasses to return the type of the subclass. Here are my interfaces:
Public Interface IBase(Of T)
Function Copy() As T
End Interface
[Code]....
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Mar 20, 2012
Are there any built in base number conversion functions in .Net specifically decimal to hex?
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Mar 16, 2012
I'm looking for a decimal to alphanumeric number base converter library in Visual Basic that does not use recursion. [url]...
which includes a demo app but discovered that it uses recursion. The problem with it using recursion became apparent when I attempted to integrate the library into my own Visual Studio Express 2010 Visual Basic project: I got a stack overflow exception.
Now I could consider increasing the size memory allocated for the stack but it might be hard to determine what this would be, given that the recursion depth might vary depending on the value to be converted.
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Mar 30, 2010
1) VB Allows non-type template parameters2) VB supports explicit specialization 3) VB allows the type parameters to be used as the base class for the generic type4) VB allows a generic type parameter itself to to be a generic 5) VB enforces that all codes are valid for all types of parametrs
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Mar 31, 2011
I have developped a usercontrol, but I can't seem to find how to databind on a property of the usercontrol in a detailsview.[code]
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Nov 27, 2010
I seem to be having a problem binding the visibility property of a textbox to a database value using the advanced binding property.I found this article (BUG: Inconsistent behavior when you bind the Visible property of a Windows Form control to a Boolean field) stating there is a bug in some ol
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Jan 25, 2010
I am a newbie at ASP.net and after using sqldatasource with a listview to insert and show results from an SQL server db I want to try using the LINQ datasource since it seems to be more flexible in codebehind.
My problem is this: I droped a listview control to the page and I created the Linq datasource in codebehind with vb. the issue that I am having when I ..Select d.columms name i get the error system.string does not contain a property with the name "columname".. if i ommit the column name then its works fine.. the funny part is the d.count works fine but after that i get the error.. please see my code below:
[Code]...
b.dbMake needs to work so that i can use Distinct ,, ia m using asp.net version:3.5 and IIS version 7.0 ..
not sure what i am missing ,, but i did try alot of approaches,,1- checked the web.config file and it seems to have two assemblies and two namespaces for LINQ..2- used different databinding syntaxs,,and i searched a lot for the solution.. the last one i read the person ommited the name of the column,, i thought that wasnt the best solution.. also my dbMake column is comming up in the "intellisence"
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Apr 26, 2012
I am creating an Extended DateTime picker. I have created a Class the inherits the Default DateTimePicker and Adds a new Property NullableValue. I have placed the control on a form and bound it to a Binding Source using the NullableValue Property. When I load the record the control updates as it should. But when I change the value and save it does not save back to the database.
[Code]...
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