Develop Reference

C# Get an object per index on an infinite list of the same object

I have an object which contain a list of this object.
when the user click on a button I want to add a new object
to one of the object in the list per an index. for example if the index is equal to 2
I want to add an object to the object.object.object(new object()).
how am I trying to get the correct object inside the inifinte object.
any better method then this one?
private void addToCommand(int indexTreeView, ClassForTest.CommadStructure CS)
{
if (_indexTreeView == 0)
{
_OCommandStructure.Add(CS);
}
else if (_indexTreeView==1)
{
_OCommandStructure[_OCommandStructure.Count - 1].SubCommandStructure.Add(CS);
}
else if (_indexTreeView == 2)
{
_OCommandStructure[_OCommandStructure.Count - 1].SubCommandStructure[_OCommandStructure[_OCommandStructure.Count - 1].SubCommandStructure.Count-1].SubCommandStructure.Add(CS);
}
}
public class CommadStructure : INotifyPropertyChanged
{
private string _Controller;;
private ObservableCollection<CommadStructure> _SubCommandStructure;
public string NameOfCommand
{
get => _NameOfCommand;
set
{
_NameOfCommand = value;
NotifyPropertyChanged();
}
}
public ObservableCollection<CommadStructure> SubCommandStructure
{
get => _SubCommandStructure;
set
{
_SubCommandStructure = value;
// NotifyPropertyChanged();
}
}
public ObservableCollection<object> Items
{
get
{
ObservableCollection<object> childNodes = new ObservableCollection<object>();
foreach (var group in this.SubCommandStructure)
childNodes.Add(group);
return childNodes;
}
}
public CommadStructure()
{
NameOfCommand = "";
}
public event PropertyChangedEventHandler PropertyChanged;
// This method is called by the Set accessor of each property.
// The CallerMemberName attribute that is applied to the optional propertyName
// parameter causes the property name of the caller to be substituted as an argument.
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

INotifyPropertyChanged and Deserialization

Given:
public class MyClass : INotifyPropertyChanged
{
public List<string> _TestFire = new List<string>();
string _StringProp;
public string StringProp
{
get
{
return _StringProp;
}
set
{
if (_StringProp != value)
{
_StringProp = value;
RaisePropertyChanged("StringProp");
_TestFire.Add("fired " + DateTime.Now);
}
}
}
}
When you serialize and then deserialize this class, it fires the RaisePropertyChanged event, which is undesirable. Is it possible to prevent this event from being fired when the class gets deserialized?
var MyclassInstance = new MyClass() { StringProp = "None" };
MyclassInstance._TestFire.Clear(); // Clear property change history
var serobj = JsonConvert.SerializeObject();
var newitem = JsonConvert.DeserializeObject<MyClass>(serobj);
// newitem._TestFire.Count == 1, the set method was executed
Is there a way to get a bool value if the class is being deserialized?
So then I could do:
set
{
if (_StringProp != value)
{
_StringProp = value;
if (!Deserializing)
{
RaisePropertyChanged("StringProp");
_TestFire.Add("fired " + DateTime.Now);
}
}
}

Yes, you can do what you want by implementing the OnDeserializing and OnDeserialized serialization callback methods in your class. In the OnDeserializing method, set your private _isDeserializing variable to true, and in OnDeserialized set it back to false. I would recommend doing the _isDeserializing check inside the RaisePropertyChanged method so you don't have duplicate code inside every property.
So you would end up with something like this:
public class MyClass : INotifyPropertyChanged
{
public List<string> _TestFire = new List<string>();
string _StringProp;
public string StringProp
{
get
{
return _StringProp;
}
set
{
if (_StringProp != value)
{
_StringProp = value;
RaisePropertyChanged("StringProp");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
// don't raise the event if the property is being changed due to deserialization
if (_isDeserializing) return;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
_TestFire.Add(propertyName + " was fired " + DateTime.Now);
}
bool _isDeserializing = false;
[OnDeserializing]
internal void OnDeserializingMethod(StreamingContext context)
{
_isDeserializing = true;
}
[OnDeserialized]
internal void OnDeserializedMethod(StreamingContext context)
{
_isDeserializing = false;
}
}
Working demo: https://dotnetfiddle.net/QkOcF4
Another way you could solve this problem is to mark your public properties with [JsonIgnore] and then mark the corresponding backing fields with [JsonProperty], specifying the property name to use in the JSON. This would allow Json.Net to set the backing fields directly and not execute any of the mutator logic.
public class MyClass : INotifyPropertyChanged
{
public List<string> _TestFire = new List<string>();
[JsonProperty("StringProp")]
string _StringProp;
[JsonIgnore]
public string StringProp
{
get
{
return _StringProp;
}
set
{
if (_StringProp != value)
{
_StringProp = value;
RaisePropertyChanged("StringProp");
_TestFire.Add("StringProp was fired " + DateTime.Now);
}
}
}
...
}
Working demo: https://dotnetfiddle.net/jc7wDu

INotifyPropertyChanged and property on BaseClass C#

I am working with WPF and MVVM model. I have a base viewmodel class called ViewModelBase. It has a property on it called Config that is a complex type. I need a derived class to be able to databind to the base class Config property in a View.
public class ViewModelBase : INotifyPropertyChanged
{
private Configuration _config;
public event PropertyChangedEventHandler PropertyChanged;
public Configuration Config
{
get { return _config; }
set
{
if(_config == null || !_config.Equals(value))
{
_config = value;
OnPropertyChanged(new PropertyChangedEventArgs("Config"));
}
}
}
public ViewModelBase()
{
}
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if(PropertyChanged != null)
{
PropertyChanged(this, e);
}
}
}
Databinding seems to be working in a read capacity, but when a property of the Config is altered in the OptionsView, the changes are not reflected in the Config itself. Any suggestions?
Configuration implementation, per request.
public class Configuration : IEquatable<Configuration>, INotifyPropertyChanged
{
private string _primaryUrl;
private string _secondaryUrl;
private DateTime _scheduledStart;
private DateTime _scheduledEnd;
private string _buffer;
private bool _isScheduleEnabled;
private int _logDays;
private int _retryDuration;
private int _maxRetryAttempts;
private string _registrationKey;
private string _email;
public string PrimaryURL
{
get { return _primaryUrl; }
set
{
if(_primaryUrl != value)
{
_primaryUrl = value;
OnPropertyChanged(new PropertyChangedEventArgs("PrimaryURL"));
}
}
}
public string SecondaryURL
{
get { return _secondaryUrl; }
set
{
if(_secondaryUrl != value)
{
_secondaryUrl = value;
OnPropertyChanged(new PropertyChangedEventArgs("SecondaryURL"));
}
}
}
public DateTime ScheduledStart
{
get { return _scheduledStart; }
set
{
if(_scheduledStart != value)
{
_scheduledStart = value;
OnPropertyChanged(new PropertyChangedEventArgs("ScheduledStart"));
}
}
}
public DateTime ScheduledEnd
{
get { return _scheduledEnd; }
set
{
if(_scheduledEnd != value)
{
_scheduledEnd = value;
OnPropertyChanged(new PropertyChangedEventArgs("ScheduledEnd"));
}
}
}
public string Buffer
{
get { return _buffer; }
set
{
if(_buffer != value)
{
_buffer = value;
OnPropertyChanged(new PropertyChangedEventArgs("Buffer"));
}
}
}
public bool IsScheduleEnabled
{
get { return _isScheduleEnabled; }
set
{
if(_isScheduleEnabled != value)
{
_isScheduleEnabled = value;
OnPropertyChanged(new PropertyChangedEventArgs("IsScheduleEnabled"));
}
}
}
public int LogDays
{
get { return _logDays; }
set
{
if(_logDays != value)
{
_logDays = value;
OnPropertyChanged(new PropertyChangedEventArgs("LogDays"));
}
}
}
public int RetryDuration
{
get { return _retryDuration; }
set
{
if(_retryDuration != value)
{
_retryDuration = value;
OnPropertyChanged(new PropertyChangedEventArgs("RetryDuration"));
}
}
}
public int MaxRetryAttempts
{
get { return _maxRetryAttempts; }
set
{
if(_maxRetryAttempts != value)
{
_maxRetryAttempts = value;
OnPropertyChanged(new PropertyChangedEventArgs("MaxRetryAttempts"));
}
}
}
public string RegistrationKey
{
get { return _registrationKey; }
set
{
if(_registrationKey != value)
{
_registrationKey = value;
OnPropertyChanged(new PropertyChangedEventArgs("RegistrationKey"));
}
}
}
public string Email
{
get { return _email; }
set
{
if(_email != value)
{
_email = value;
OnPropertyChanged(new PropertyChangedEventArgs("Email"));
}
}
}
public Configuration() { }
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if(PropertyChanged != null)
{
PropertyChanged(this, e);
}
}
}
Here is one of the culprit bindings:
<xctk:DateTimePicker Grid.Column="1" Value="{Binding Config.ScheduledStart}" Height="20" VerticalAlignment="Top"/>

The INotifyPropertyChanged implementation only applies to the class directly. So in your case, to the ViewModelBase class and its subtypes.
In this case, the PropertyChangedEvent is raised in the setter of the Config property, so whenever the Config property is set (and the setter is called), the event is raised.
This however does not mean that when mutating the Config object that the even is also raised. In general, this is not the case.
In order to raise the event when the Config object is changed, you would have to reassign the object to the view model (calling the setter again). This however does not work when data binding to the object.
A better solution is to make the Configuration implement INotifyPropertyChanged interface itself. So when a property within that object is changed, an event is raised as well. WPF will also recognize this for subobjects, so it will automatically work.

Databinding seems to be working in a read capacity..
Which is fine but if you want a change capacity, then the class Configuration will have to adhere to INotifyPropertyChanged and each property on the class needs to report PropertyChange notifications for any changes to be shown in bound xaml controls.
but when a property of the Config is altered in the OptionsView, the changes are not reflected
What you have now only notifies if the instance of Configuration has been replaced; not individual property changes within the current instance.

Refresh an ObservableCollection (overwrite)

How can I refresh the following ObservableCollection?
public class ViewModelProperties
{
private ObservableCollection<ServerProperties> properties;
public ObservableCollection<ServerProperties> Properties
{
get
{
properties = new ObservableCollection<ServerProperties>();
for (var lineNumber = 0; lineNumber < MainWindow.lineCount; lineNumber++)
{
if (MainWindow.textProperties[lineNumber, 0] == null) break;
properties.Add(new ServerProperties(MainWindow.textProperties[lineNumber, 0],
MainWindow.textProperties[lineNumber, 1]));
}
return properties;
}
}
}
public class ServerProperties
{
private string property;
private string value;
public ServerProperties()
{
}
public ServerProperties(string property, string value)
{
Property = property;
Value = value;
}
public string Property
{
get
{
return this.property;
}
set
{
this.property = value;
}
}
public string Value
{
get
{
return this.value;
}
set
{
this.value = value;
}
}
public override string ToString()
{
return string.Format("[Property : {0}]", Value);
}
}
I changed the value of textProperties[,] and now I'd like to overwrite the previous content of the collection with the current content of textProperties[,].
What would be the simplest way to do this?
Any help would be appreciated.

Start off by implementing INotifyPropertyChanged in your ViewModel as well as in the ServerProperties object. This way you can raise the PropetyChanged event which will pass back to the user interface.
ViewModel
public class ViewModelProperties : INotifyPropertyChanged {
public event ProeprtyChangedEventHandler PropertyChanged;
private ObservableCollection<ServerProperties> properties = new ObservableCollection<ServerProperties>();
public ObservableCollection<ServerProperties> Properties {
get { return properties;}
set {
properties = value;
this.RaisePropertyChangedEvent("Properties");
}
}
private void RaisePropertyChanged(string propertyName) {
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Implementing this on the ServerProperties object as well will allow you to change the objects, at any level, and have it bubble up to the interface.
Lastly look into your population code and in order to get the property to update successfully first populate it to a List then re-initialise the ObservableCollection using the List.
Properties = new ObservableCollection<ServerProperties>(propertiesList);
This also allows you to better handle the creation of your ObservableCollection and perform tests before posting the output to the interface. Hope it helps.

For example, one of the simpler solutions could be
public class ViewModelProperties
{
private ObservableCollection<ServerProperties> properties = new ObservableCollection<ServerProperties>();
public ObservableCollection<ServerProperties> Properties
{
get
{
return properties;
}
}
public void SetProperties()
{
properties.Clear();
for (var lineNumber = 0; lineNumber < MainWindow.lineCount; lineNumber++)
{
if (MainWindow.textProperties[lineNumber, 0] == null) break;
properties.Add(new ServerProperties(MainWindow.textProperties[lineNumber, 0],
MainWindow.textProperties[lineNumber, 1]));
}
}
}
Any time you wish to add new items to OC, just call the SetProperties method.

how to prevent infinite property change

Lets say I have sales price, down payment amount, down payment percent and loan amount. When any of these properties are changed by the user the others need to be updated to reflect the new values. How do you deal with this type of infinite property change events?

When flow control is necessary across multiple attributes, I'll institute a flow control variable - a boolean - and in each property that's being changed, I'll add a test to see if I'm under flow control or not.
private bool controlledChange = false;
public property int MyVal1
{
set
{
_myVal1 = value;
if(!controlledChange)
{
controlledChange = true;
MyVal2 -= 1;
controlledChange = false;
}
}
}
public property int MyVal2
{
set
{
_myVal2 = value;
if(!controlledChange)
{
controlledChange = true;
MyVal1 += 1;
controlledChange = false;
}
}
}
This way whatever property is changed can initiate changes across the other properties, but when they get changed, they will no NOT to initiate their own set of changes in turn.
You should also look to make as many of those properties read only as possible, if they can have calculated results, so that you limit how the object can be changed.

THe easiest way is to only raise a change event if the property has really changed:
public decimal SalePrice {
get{
return salePrice;
}
set {
if (salePrice != value) {
salePrice = value; // putting as first statement prevents the setter
// to be entered again ...
RaiseSalePriceChange();
// Set other properties
}
}
}

I'm not sure I completely understand, since I don't know what you mean by 'infinite'
This may be a good use case for actually backing your properties with fields. That way, you can trigger events on Property sets, but internally set the fields one at a time without triggering N events.
class MyClass
{
private string m_Name;
private int m_SomeValue;
public string Name
{
get { return m_Name; }
set
{
if (value != m_Name)
{
m_Name = value;
m_SomeValue++;
// Raise Event
}
}
}
public int SomeValue
{
get { return m_SomeValue; }
set
{
if (m_SomeValue != value)
{
m_SomeValue = value;
// Raise Event
}
}
}

If INotifyPropertyChanged is really needed to notify external objects, so I would just centralise everything. Like this:
private double salesPrice;
private double downPaymentAmount;
private double downPaymentPercent;
private double loanAmount;
public double SalesPrice
{
get
{
return salesPrice;
}
set
{
if (salesPrice != value)
{
salesPrice = value;
// maybe you would rather use a RecalculateForSalePriceChanged() method
RecalculateDownPaymentAmount();
RecalculateDownPaymentPercent();
RecalculateLoanAmount();
propertiesChanged();
}
}
}
public double DownPaymentAmount
{
get
{
return downPaymentAmount;
}
set
{
if (downPaymentAmount != value)
{
downPaymentAmount = value;
// see above
RecalculateDownPaymentPercent();
RecalculateLoanAmount();
RecalculateSalesPrice();
propertiesChanged();
}
}
}
public double DownPaymentPercent
{
get
{
return downPaymentPercent;
}
set
{
if (downPaymentPercent != value)
{
downPaymentPercent = value;
// see above
RecalculateDownPaymentAmount();
RecalculateLoanAmount();
RecalculateSalesPrice();
propertiesChanged();
}
}
}
public double LoanAmount
{
get
{
return loanAmount;
}
set
{
if (loanAmount != value)
{
loanAmount = value;
// see above
RecalculateDownPaymentAmount();
RecalculateDownPaymentPercent();
RecalculateSalesPrice();
propertiesChanged();
}
}
}
private void propertiesChanged()
{
RaisePropertyChanged("SalesPrice", "DownPaymentAmount", "DownPaymentPercent", "LoanAmount");
}
Maybe you can concentrate the recalculations in less methods or even a single one, but I do not know how you calculate them. But certainly you have to keep a specific order when recalculating the values.
Since they only operate on fields and do not change the properties, there will be no PropertyChanged-feedback-loop.
Hope this helps and I did not misunderstood what you wanted.

What the OP wanted was something like following
class A : INotifyPropertyChanged
{
private int field1;
public int Property1
{
get { return field1; }
set
{
field1 = value;
field2++;
RaisePropertyChanged("Property1");
RaisePropertyChanged("Property2");
}
}
private int field2;
public int Property2
{
get { return field2; }
set
{
field2 = value;
field1++;
RaisePropertyChanged("Property1");
RaisePropertyChanged("Property2");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
What he might be doing was handling other properties in the setter of each property he mentioned thus leading to cyclic invocation of setters.
Vijay