I have a simple custom class (Person), which I want to bind to a label as a whole (not to separate properties of this class). The label should just present whatever the Person.ToString() returns (in this case FirstName + LastName).
How do I properly bind it using the person as a Source.
How do I make sure that any change in one of the properties of the Person will be reflected in the label?
public class Person : INotifyPropertyChanged {
private string firstName;
public string FirstName {
get {
return firstName;
}
set {
firstName = value;
OnPropertyChanged("FirstName");
}
}
private string lastName;
public string LastName {
get {
return lastName;
}
set {
lastName = value;
OnPropertyChanged("LastName");
}
}
public override string ToString() {
return FirstName + " " + LastName;
}
private void OnPropertyChanged(string name) {
if (PropertyChanged != null) {
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
public Window1() {
myPerson = new Person() {
FirstName = "AAA",
LastName = "BBB"};
InitializeComponent();
}
public Person MyPerson {
get {
return myPerson;
}
set {
myPerson = value;
}
}
Label Content="{Binding Source=MyPerson}"
Create a new property FullName which returns the full name and raise PropertyChanged for FullName in the setters of FirstName and LastName as well. You should never bind to the object itself.
Related
I have the following classes
public abstract class Contact
{
public abstract string FullName { get; }
public abstract string FullName_LastNameFirst { get; }
}
public class PersonContact
{
private string firstName;
private string lastName;
public override string FullName => firstName + " " + lastName;
public override string FullName_LastNameFirst => lastName + ", " + firstName;
}
public class BusinessContact
{
private string name;
public override string FullName => name;
public override string FullName_LastNameFirst => name;
}
These classes extend INotifyPropertyChanged (not shown) and include public properties wrapping the private variables that trigger OnPropertyChanged.
The question is if I bind in WPF to the FullName or FullName_LastNameFirst properties how can I have them update when either of the properties that they are wrapping are changed.
When you change underlying private fields (firstName, lastName or name in BusinessContact) - call
OnPropertyChanged("FullName");
OnPropertyChanged("FullName_LastNameFirst");
WPF data binding will subscribe to PropertyChanged event of your object and will listen to change notifications of corresponding property. Since your property has no setter in which you can call OnPropertyChanged - you need to call it explicitly when any underlying data changes.
You surely have properties for your Person. If you have a ForeName property you can implement it like:
private string _ForeName;
public string ForeName
{
get
{ return _ForeName; }
set
{
if (_ForeName != value)
{
_ForeName = value;
OnPropertyChanged(nameof(this.ForeName));
OnPropertyChanged(nameof(this.FullName));
}
}
}
As you can see, a PropertyChanged event will be fired, if the value of ForeName is changed. You can make the LastName property similar.
An other solution is, if the person class listens to its own PropertyChanged:
public Person()
{
this.PropertyChanged += this.Person_PropertyChanged;
}
private void Person_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == nameof(LastName))
{
this.OnPropertyChanged(nameof(FullName));
}
if (e.PropertyName == nameof(ForeName))
{
this.OnPropertyChanged(nameof(FullName));
}
}
This second solution is useful if you have generated classes, and you cannot change the property setters. Then you can make a partial class, and handle the property changes.
The answers from Evk and lvoros are technically correct.
However, you can save yourself from having to write all this boilerplate code by using the Fody ProperyChanged library (available via Nuget).
A class written as
public class Person : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public string GivenNames { get; set; }
public string FamilyName { get; set; }
public string FullName => $"{GivenNames} {FamilyName}";
}
Will actually be compiled as
public class Person : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
string givenNames;
public string GivenNames
{
get => givenNames;
set
{
if (value != givenNames)
{
givenNames = value;
OnPropertyChanged("GivenNames");
OnPropertyChanged("FullName");
}
}
}
string familyName;
public string FamilyName
{
get => familyName;
set
{
if (value != familyName)
{
familyName = value;
OnPropertyChanged("FamilyName");
OnPropertyChanged("FullName");
}
}
}
public string FullName => $"{GivenNames} {FamilyName}";
public virtual void OnPropertyChanged(string propertyName)
{
var propertyChanged = PropertyChanged;
if (propertyChanged != null)
{
propertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Fody will automatically generate OnPropertyChanged() calls for any dependent calculated properties in addition to the direct property wrappers.
I'm not normally a fan of programs working by "magic", but Fody is my one expception.
I have a ComboBox that contains a list of names: LastName + ", " + FirstName.
When a name is selected, it populates two text boxes with the First and Last names, respectively.
What I am trying to do is, if the name is changed in the text boxes, I want the change to be updated to the ComboBox as well without having to reload the entire thing. My ComboBox is NOT loaded directly from a database, so I cannot use RefreshItem()
Is this even possible?
You could implement the INotifyPropertyChanged interface and use a BindingSource as the DataContext of your ComboBox. Please refer to the following sample code.
Person.cs:
public class Person : INotifyPropertyChanged
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set { _firstName = value; NotifyPropertyChanged(); }
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set { _lastName = value; NotifyPropertyChanged(); }
}
public string FullName { get { return LastName + ", " + FirstName; } }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Form1.cs:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
List<Person> people = new List<Person>()
{
new Person() { FirstName = "Donald", LastName = "Duck" },
new Person() { FirstName = "Mickey", LastName = "Mouse" }
};
BindingSource bs = new BindingSource();
bs.DataSource = people;
comboBox1.DataSource = bs;
comboBox1.DisplayMember = "FullName";
textBox1.DataBindings.Add(new Binding("Text", bs, "FirstName", false, DataSourceUpdateMode.OnPropertyChanged));
textBox2.DataBindings.Add(new Binding("Text", bs, "LastName", false, DataSourceUpdateMode.OnPropertyChanged));
}
}
In WPF, I want to create three textboxes for the properties: FullName, FirstName and LastName. The text for these textboxes will be based on the listbox on the left (as shown in the program image below). I'm already done with getting text from the listbox to the textbox but I want to sync the values for the names such that:
changing the value for FullName, changes the listbox, FirstName and LastName box
and changing the value for FirstName and LastName changes the FullName and listbox
Here is what the program looks like:
(Program image)
OK thanks to Jared,I was able to solve the problem by making small changes to his answer but I dont like my solution lol can someone suggest a better revision to this program?
class Student : INotifyPropertyChanged
{
private string name;
public string Name
{
get
{
return name;
}
set
{
FirstName = value.Split(" ".ToCharArray())?[0];
LastName = value.Split(" ".ToCharArray())?[1];
OnPropertyChanged("Name");
OnPropertyChanged("FirstName");
OnPropertyChanged("LastName");
}
}
private string firstName;
public string FirstName
{
get
{
return firstName;
}
set
{
firstName = value;
name = value + " " + LastName;
OnPropertyChanged("FirstName");
OnPropertyChanged("Name");
}
}
private string lastName;
public string LastName
{
get
{
return lastName;
}
set
{
lastName = value;
name = FirstName + " " + value;
OnPropertyChanged("LastName");
OnPropertyChanged("Name");
}
}
private Course _course;
public Course Course
{
get { return _course; }
set
{
_course = value;
OnPropertyChanged("Course");
}
}
private int _age;
public int Age
{
get { return _age; }
set
{
_age = value;
OnPropertyChanged("Age");
}
}
private DateTime _birthday;
public DateTime Birthday
{
get { return _birthday; }
set
{
_birthday = value;
OnPropertyChanged("Birthday");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
I believe what you'll need is a class such as the one below. You'd then bind your listbox to a collection of these, and the form elements to the currently selected item.
I added a space between first and last name. If you want that removed, you'll need to find another way of splitting the first and last names, such as checking capitalization.
Since FullName will be set regardless of which property is modified, I put all the FirePropertyChanged calls in its setter. I haven't tested this, but I assume it will work. :)
EDIT: Changed FullName setter to set the private variable of firstName and lastName instead of the public property.
public class Student : INotifyPropertyChanged
{
public string FullName
{
get
{
return FirstName + " " + LastName;
}
set
{
firstName = value.Split(" ".ToCharArray())?[0];
lastName= value.Split(" ".ToCharArray())?[1];
FirePropertyChanged("FullName");
FirePropertyChanged("FirstName");
FirePropertyChanged("LastName");
}
}
private string firstName;
public string FirstName
{
get
{
return firstName;
}
set
{
firstName = value;
FullName = value + " " + LastName;
}
}
private string lastName;
public string LastName
{
get
{
return firstName;
}
set
{
lastName = value;
FullName = FirstName + " " + value;
}
}
public void FirePropertyChanged (string PropertyName)
{
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(PropertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
I have two listboxes. One source listbox which is binded to ObservableCollection<Person> MyNetwork The other listbox is my target listbox which is binded to ObservableCollection<Person> Crew.Each time I drop the item in the target listbox I create a new instance of the sourceItem.
Now I would like to update the properties of new istances, but it doesn't seem to work. Is there a way to make the copies of the sourceItems to update when I change one of the sourceItems(FirstName) properties. I'm pretty new to WPF and MVVM and wonder if this is possible or is there a work around to achieve this?
Here what I have so far:
in the ViewModel
Source ListBox:
private ObservableCollection<Person> _myNetwork = new ObservableCollection<Person>();
public ObservableCollection<Person> MyNetwork
{
get { return _myNetwork; }
set { _myNetwork = value; RaisePropertyChanged(); }
}
Target ListBox:
private ObservableCollection<Person> _crew = new ObservableCollection<Person>();
public ObservableCollection<Person> Crew
{
get { return _crew; }
set { _crew = value; RaisePropertyChanged("Crew");}
}
void IDropTarget.Drop(IDropInfo dropInfo)
{
Person sourceItem = dropInfo.Data as Person;
if (dropInfo.Data is Person)
{
Person person = new Person(sourceItem.FirstName,
sourceItem.LastName,
sourceItem.Profession);
Crew.Add(person);
}
}
The Model:
public Person(string FirstName, string LastName, string Profession)
{
_firstName = FirstName;
_lastName = LastName;
_profession = Profession;
}
private string _firstName;
public string FirstName
{
get { return this._firstName; }
set { this._firstName = value; RaisePropertyChanged("FirstName"); }
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set { _lastName = value; RaisePropertyChanged("LastName"); }
}
private string _profession;
public string Profession
{
get { return _profession; }
set { _profession = value; RaisePropertyChanged("Profession"); }
}
I would recommend using a library that wraps the PropertyChanged event so it's easier to update your properties when you need to call them.
Once example is Caliburn for WPF. You can use NotifyOfPropertyChange(() => FirstName) from within your code to update the FirstName property however you need to (it doesn't have to just be used in the setter).
Here is a good article on how to use it.
Example:
using Caliburn.Micro;
namespace CaliburnMicroExample
{
public class ShellViewModel : PropertyChangedBase
{
private string _message;
public string Message
{
get { return _message; }
set
{
_message = value;
NotifyOfPropertyChange(() => Message);
}
}
public ShellViewModel()
{
Message = "Hello World";
}
}
}
I have an ObservableCollection<Person> in my viewmodel. This is bound as an ItemsSource to a DataGrid in the view. The class Person only has threeProperties:
public class Person : ViewModelBase
{
private Guid id;
public Guid Id
{
get { return this.id; }
set
{
this.id = value;
OnPropertyChanged("Id");
}
}
private string firstname;
public string Firstname
{
get { return this.firstname; }
set
{
this.firstname = value;
OnPropertyChanged("Firstname");
}
}
private string lastname;
public string Lastname
{
get { return this.lastname; }
set
{
this.lastname = value;
OnPropertyChanged("Lastname");
}
}
}
The class ViewModelBase implements INotifyPropertyChanged.
The items in the collection are updated perfect if I add or remove an entry in the dategrid. The item is then also removed in the collection.
My problem is that the content of an person-item is updated, but I don't know how I can react on this.
Do I have to add an event or something else to the person-class to get informed or is there another way to do this?
Implement INotifyPropertyChanged interface on your class Person so that any change in Person properties gets reflected back on UI.
Sample -
public class Person : INotifyPropertyChanged
{
private Guid id;
public Guid Id
{
get { return id; }
private set
{
if(id != value)
{
id = value;
NotifyPropertyChanged("Id");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}