I have a control with a inner TextBox. I want to make a direct relationship between the Text property of the UserControl and the Text property of the TextBox. The first thing I realized is that Text was not being displayed in the Properties of the UserControl. Then I added the Browsable(true) attribute.
[Browsable(true)]
public override string Text
{
get
{
return m_textBox.Text;
}
set
{
m_textBox.Text = value;
}
}
Now, the text will be shown for a while, but then is deleted. This is because the information is not written automatically within the xxxx.Designer.cs file. How can this behviour be changed?
You need more attributes:
[EditorBrowsable(EditorBrowsableState.Always)]
[Browsable(true)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
[Bindable(true)]
public override string Text { get; set; }
Reflector is a crucial tool for a .NET developer. It is immediately obvious what you need to do when you use it to look at the UserControl.Text property:
[Bindable(false), EditorBrowsable(EditorBrowsableState.Never), Browsable(false),
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public override string Text
{
get
{
return base.Text;
}
set
{
base.Text = value;
}
}
Ho showed you what you need to do to cancel these attributes, too bad he didn't show you how he found out. Reflector is was free, download it from redgate.com or check the alternatives here : Something Better than .NET Reflector?
For serialization within the InitializeComponent(), all you need is the DesignerSerializationVisibilityAttribute:
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
Related
well, i'm trying to make a custom view which is like user thumbnail view.
the view(ViewCell?) displays UserModel(my custom model)'s thumbnail + username.
this is the code in UploaderCell.xaml.cs
public static readonly BindableProperty UploaderProperty =
BindableProperty.Create(
propertyName: "Uploader",
returnType: typeof(UserModel),
declaringType: typeof(UploaderCell)
);
public UserModel Uploader
{
get
{ return GetValue(UploaderProperty) as UserModel; }
set
{ SetValue(UploaderProperty, value); }
}
and this is used like <UploaderCell Uploader="{Binding post.uploader}"/>
in some where else.
and the error i get is System.InvalidCastException Class
it's not my mistake about actually passing the wrong data.
so my question is, is it impossible to make BindableProperties with non basic types(string, int ,ect..)?
Yes, it is possible to use complex types and is something I do all the time. What you have posted of your code looks correct.
I would check the code in your view model to see what you are actually binding to that value as that might be the cause of your error. If you are binding the wrong type then that might lead to the error.
Make sure your data model has
{ get; set; }
this..
ah..
I have a Xamarin.Forms xaml page in which I am using a ListView to allow the user to pick a single item out of a list. I have bound the ListView's SelectedItem property to a property on my ViewModel and this works fine. As soon as the user changes the selected item the property in my viewmodel updates as well.
However, even though I initially set the property in my ViewModel to one of the values from the list, when the page loads the ListView's SelectedItem property is null, which in turn sets the ViewModel property to null as well.
What I need is the other direction, I want the ListView to initially select the item that i've set in the VM property.
I can hack together a solution by writing extra code in the code behind file to explicitly set the initial selected item, but this introduces additional properties and complexity and is quite ugly.
What is the correct way to set the initial selected item of a ListView who's selected item is bound to a viewmodel property?
-EDIT-
I was asked to provide the code that I'm using for my binding.
It's very simple, standard:
<ListView x:Name="myList" ItemsSource="{Binding Documents}" SelectedItem="{Binding SelectedDocument}">
the view model that is set as the binding context for the listview is instantiated before the page is created and looks like this:
public class DocumentSelectViewModel : ViewModelBase
{
private Document selectedDocument;
public List<Document> Documents
{
get { return CachedData.DocumentList; }
}
public Document SelectedDocument
{
get { return selectedDocument; }
set { SetProperty(ref selectedDocument, value);
}
public DocumentSelectViewModel()
{
SelectedDocuement = CachedData.DocumentList.FirstOrDefault();
}
}
SetProperty is a function which simply rasies the INotifyPropertyChanged event if the new value is different from the old one, classical binding code.
I am a little rusty on XAML but don't you need to make the binding two-way?
E.G.
{ Binding SelectedDocument, Mode=TwoWay }
As long as the SelectedDocument property change raises the INotifyPropertyChanged event then you should get the desired effect.
If you replace
public DocumentSelectViewModel()
{
SelectedDocument = CachedData.DocumentList.FirstOrDefault();
}
By
public DocumentSelectViewModel()
{
SelectedDocument = Documents.FirstOrDefault();
}
Does it work for you ?
I had a similar problem that has been resolved this way...
You can use ctor DocumentSelectViewModel for set initial value. Honestly I dont like to make some job in ctor block but Xamarin.... You dont need DocumentSelectViewModel method. It will work.
public DocumentSelectViewModel ()
{
SelectedDocument = Documents[0]; //or any your desired.
}
I know this is a weird one but bear with me. I need to set a default state/value for form inputs on a portion of my application.
In my "MainController" I pull up a portion (or 'wrapper' of sorts) page and then pull partial views from this main page. Here's a pseudo-code example:
User goes to Main ->
MainController/Index Called
-> User clicks Link A ->
AJAX .load() pulls html from PartialViewA into #partialContainer
-> User clicks Link B ->
AJAX .load pulls html from PartialViewB into #partialContainer
Here's the AJAX call:
$("#mainPanel").load('#Url.Action("GetModule","Settings")' + '?partialName=' + moduleName);
...and the corresponding server-side action that handles it:
public ActionResult GetModule(string partialName)
{
return PartialView(partialName);
}
It works great for me, each of the modules has plenty of form fields on them, all interacting well with one another and server so that isn't my problem. The issue is setting default values from the dbase for the form fields contained in the partial views.
For instance the "General" partial has many checkboxes which will determine how portions of the application display. I want to pull from the database the pre-exisiting boolean value and when the partial gets pulled from GetModule(), have these values defaulted.
I've taken a look around and I'm afraid the way that I am pulling the partial's into the main page may be the issue. I thought I could build the defaults into the constructor like so:
public class GeneralViewModel
{
public GeneralViewModel()
{
var Data = from m in dataContext.Table
where m.UserID == _id
select new
{
m.Data1,
m.Data2,
};
foreach(var setting in Data)
{
Checkbox1 = Convert.ToBoolean(setting.Data1); // Conversion from bool? to bool
Checkbox2 = Convert.ToBoolean(setting.Data2); // Conversion from bool? to bool
}
}
public bool Checkbox1 { get; set; }
public bool Checkbox2 { get; set; }
}
But it would appear the constructor never gets called. That sort of makes sense, except when you consider the fact that my form fields are not only rendering properly, but communicating with the database just fine as well. So the question is, what am I doing wrong? Is it the way I call the Partial's or am I missing something with assigning values to my VM values?
As always, thanks SO!
I think it's better to have different action methods for rendering the partial views, but for your case, i think this solution would work.
Have a Model that contains the other view models
public class ViewModel
{
public ViewModel1 ViewModel1 { get;set;}
public GenereViewModel General {get;set;}
}
Then in your controller you could initialize the viewmodel based on the partial name.
public ActionResult GetModule(string partialName)
{
var model = new ViewModel();
switch (partialName)
{
case "General": model.General = InitializeGeneral();
break;
case "ViewModel1": model.ViewModel1 = InitializeViewModel1(); break;
}
return PartialView(partialName, model);
}
private GeneralViewModel InitializeGeneral()
{
// initalize then return model
}
I created a Data Source with VB.NET and Visual Studio 2005. I dragged the data source onto my dialog, and VS created the text boxes with the members of my linked Object, a System.Windows.Forms.BindingSource and a System.Windows.Forms.BindingNavigator.
I populate the List (called myList), set myList as the DataSource in the BindingSource, and things work peachy except for the fact that I want this to be read-only. If the user changes something in one of the text boxes, it saves the changes.
I tried creating a read-only collection to bind to the BindingSource, but that didn't solve the problem:
Dim detailsDlg As New dlgMyDetails
Dim readOnlyList As New ReadOnlyCollection(Of MyObjects)(myList)
detailsDlg.MyBindingSource.DataSource = readOnlyList
detailsDlg.ShowDialog()
I guess I could disable all of the text boxes, but that seems a bit heavy-handed, plus I'd probably want to change the font color so that it's easier to read.
Ideally, I probably wouldn't care if users were able to set focus to the text boxes, or even edit the contents, but I just wouldn't want any changes to persist. That is, if someone edited something, used the navigator to go to the next record, and then returned, I'd want it as it was before the user played with it.
Any suggestions / guidance?
Thanks in advance!
From a Model-View-Control perspective, the constraint you want is not on the model or control, but the view. The view should restrict what is editable on the screen.
If it truly is read-only, why not go with a read-only user interface element, ie, a label? The reason you do this is to reduce confusion to the user. If it is a textbox, there is a reasonable expectation that at some point the data becomes editable. If this is not the case, then presenting a disabled textbox is likely not the right UI element to present, rather, as mentioned, a label.
Instead of making a ReadOnlyCollection you can change the property in your class (MyObjects) to ReadOnly or add attribute System.ComponentModel.ReadOnly(true) to your property, example:
class Person
{
public Person(int id, string name, string address)
{
_id = id;
Name = name;
Address = address;
}
private int _id = 0;
public int ID { get { return _id; } }
[System.ComponentModel.ReadOnly(true)]
public string Name { get; set; }
public string Address { get; set; }
}
ID and Name is going to be readonly, sorry if the example is in C#. Hope this helps.
Cheers.
I have a class
public class Item
{
public string A { get; set; }
public Control B { get; set; }
}
I'm using MVVM with Silverlight. I have a custom view that is inherited from a standard view. Custom view has public property public ICollection MyItems { get; set; } which should store items described above.
In xaml of my view I have
xxxx.MyItems>
Item A="someText" B="_existingButton" />
Item A="someText2" B="_existingButton2" />
/xxxx.MyItems>
Initialize() method of View fails when trying to assign value for B.
How can I assign a reference to existing element for a custom collection item?
I don't exactly understand what you are trying to achieve, but to help you arrive at a solution, I recommend that you attempt your task in the code behind file first (i.e. in the .xaml.cs) file.
By doing this, you will be given much more informative help from the compiler and intellisense.
Once you've achieved what you wanted in the code behind, then try and implement it in the xaml file.