As the topic suggests I have some problems with PropertyInfo.SetValue. To get to the point, here is my example - I have created my own class and the main thing about it is the presentation object:
using System;
using System.Reflection;
namespace TestingSetValue
{
public class Link
{
private object presentationObject = null;
private string captionInternal = string.Empty;
public Link (string caption)
{
captionInternal = caption;
}
public string CaptionInternal
{
get { return captionInternal; }
set { captionInternal = value; }
}
public bool Visible
{
get
{
if (PresentationObject != null)
{
PropertyInfo pi = PresentationObject.GetType().GetProperty("Visible");
if (pi != null)
{
return Convert.ToBoolean(pi.GetValue(PresentationObject, null));
}
}
return true;
}
set
{
if (PresentationObject != null)
{
PropertyInfo pi = PresentationObject.GetType().GetProperty("Visible");
if (pi != null)
{
pi.SetValue(PresentationObject, (bool)value, null);
}
}
}
}
public object PresentationObject
{
get { return presentationObject; }
set { presentationObject = value; }
}
}
}
Then, I do this:
private void btnShowLink_Click(object sender, EventArgs e)
{
Link link = new Link("Here I am!");
this.contextMenu.Items.Clear();
this.contextMenu.Items.Add(link.CaptionInternal);
link.PresentationObject = this.contextMenu.Items[0];
link.Visible = true;
lblCurrentVisibility.Text = link.Visible.ToString();
}
Now, I can imagine this doesn't look too logical/ economical, but it shows the essence of my real problem. Namely, why doesn't the visibility of presentation object (and the value of link.Visible) change, after I call:
link.Visible = true;
I simply do not know what else to do to make this work... Any help is deeply appreciated.
To make things even more interesting, the property Enabled behaves as expected of it...
PropertyInfo pi = PresentationObject.GetType().GetProperty("Enabled");
Could it be related to the fact that Visible is actually a property of ToolStripDropDownItem base base object, whereas Enabled is 'direct' property of ToolStripDropDownItem ?
It would have been easier to figure this out if you said upfront what class this is but now we know it is ToolStripDropDownItem which we can infer means WinForms.
What you are seeing is an oddity with the ToolStripItem's Visible property. It's setter & getter are not tied directly together. MSDN says
"The Available property is different from the Visible property in that
Available indicates whether the ToolStripItem is shown, while Visible
indicates whether the ToolStripItem and its parent are shown. Setting
either Available or Visible to true or false sets the other property
to true or false."
In other words, you want to use the Available property instead of the Visible property
Check http://msdn.microsoft.com/en-us/library/system.web.ui.control.visible.aspx. Maybe this is causing your problem.
There is very important piece of info:
If this property is false, the server control is not rendered. You should take this into account when organizing the layout of your page. If a container control is not rendered, any controls that it contains will not be rendered even if you set the Visible property of an individual control to true. In that case, the individual control returns false for the Visible property even if you have explicitly set it to true. (That is, if the Visible property of the parent control is set to false, the child control inherits that setting and the setting takes precedence over any local setting.)
Related
I have the following code in the ViewModel class, in the constructor where I define that the buttons are always Enabled = false when starting the form ...
public partial class EditarConceptoWindow : ChildWindow
{
public EditarConceptoWindow(string documentoId)
{
InitializeComponent();
viewModel.Saved += new EventHandler<Microsoft.Practices.Prism.Events.DataEventArgs<bool>>(ViewModel_Saved);
viewModel.Calculation += new EventHandler<Microsoft.Practices.Prism.Events.DataEventArgs<bool>>(ViewModel_Calculation);
this.DataContext = viewModel;
BtnCalcular.IsEnabled = false;
BtnObtenerTCRM.IsEnabled = false;
....... rest of code
In a checked event of a check box when placing the Selected check box, it must be enabled to be set to true, depending on whether a particular element of a combobox has been selected as well;
private void cbAgregarManual_Checked(object sender, RoutedEventArgs e)
{
if (this.ComboConcepto.SelectedValue.ToString() == "DPI")
{
BtnCalcular.IsEnabled = true;
BtnObtenerTCRM.IsEnabled= true;
}
}
This must be done if and only if the checkbox is clicked and the DPI value is selected in the combobox.
But the behavior of the buttons is that when starting the form they are always IsEnabled = true and if the checkbox control is clicked if it works but I can't find a reason because only until I click the checkbox it works, there are some controls (such as TextBoxes, and also the buttons) with this directive in the XAML.
IsEnabled="{Binding ElementName=cbAgregarManual, Path=IsChecked }"
I suggest that you centralize the logic of the enabling into one property to avoid this mismatch of logic setting confusion.
In this new property it will use INotifyPropertyChanged for the notification of that change, but called in from other properties. So to sum up, when any of the associated values change, they do the notify call on the logic property; that process ensures that the control is properly en/dis-abled.
Example
Such as this pseudo code where I check three different other properties:
public bool IsEnabledCombo { get { return ClickStatus
&& OtherStatus
&& !string.IsNullOrEmpty( UserText); }
public bool ClickStatus { get { return _clickStatus; }
set { _clickStatus = value;
NotifyPropertyChanged("ClickStatus");
NotifyPropertyChanged("IsEnabledCombo");
}}
public bool OtherStatus { get { return _otherStatus; }
set { _clickStatus = value;
NotifyPropertyChanged("OtherStatus");
NotifyPropertyChanged("IsEnabledCombo");
}}
public string UserText { ...
set { _userText = value;
NotifyPropertyChanged("UserText");
NotifyPropertyChanged("IsEnabledCombo");
Bind your control as such
IsEnabled="{Binding IsEnabledCombo }"
So wherever one of the related values can change they also call NotifyPropertyChanged("IsEnabledCombo"); and the control status is updated automatically.
I provide a another notify chained example doing similar on my blog:
Xaml: ViewModel Main Page Instantiation and Loading Strategy for Easier Binding
I have created a C# User Control in Visual Studio 2019. It has a property called "BoundLayout".
public Layout BoundLayout
{
get
{
return _Layout;
}
set
{
_Layout = value as Layout;
if (_Layout == null)
{
MessageBox.Show("Value submitted is not of type 'LAYOUT'","Invalid Value",MessageBoxButtons.OK,MessageBoxIcon.Error);
}
else
{
InitializeControl();
}
}
}
If a program attempts to assign an incompatible value to the property an error message is displayed in a MessageBox. This works correctly.
What is very strange is that when ever I BUILD (not RUN) the project this error message is displayed in its modal MessageBox which must be acknowledged before you can return to Visual Studio. This occurs when building in both Debug and Release modes. A break point added to the property set code does not get triggered. The build completes successfully without errors or warnings and I can run the application.
The application, including this User Control operates as intended. I have never encountered this behavior before. Has anyone else?
The complete (still in development) code for the User Control:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Dispatcher
{
public partial class DivisionModuleGrid : UserControl
{
private Layout _Layout = null;
private ObservableListSource<LayoutDivision> _LayoutDivisions;
private DivisionModulesList _activeDivision = null;
private int _divisionCount;
public Layout BoundLayout
{
get
{
return _Layout;
}
set
{
_Layout = value as Layout;
if (_Layout == null)
{
MessageBox.Show("Value submitted is not of type 'LAYOUT'","Invalid Value",MessageBoxButtons.OK,MessageBoxIcon.Error);
}
else
{
InitializeControl();
}
}
}
public DivisionModulesList ActiveDivision
{
get
{
return _activeDivision;
}
set
{
_activeDivision = value as DivisionModulesList;
if (_activeDivision != null)
{
lbl_ActiveDivision.Text = _activeDivision.DivisionName;
}
else
{
lbl_ActiveDivision.Text = "-No Active Division-";
}
}
}
public DivisionModuleGrid()
{
InitializeComponent();
}
private void InitializeControl()
{
_LayoutDivisions = _Layout.LayoutDivisions;
_divisionCount = _LayoutDivisions.Count;
tbx_LayoutName.Text = _Layout.LayoutName;
// Grid Layout divide into Rows & Columns
int tlp_rows = _divisionCount / 3;
TableLayoutPanel tlp = (TableLayoutPanel)(Controls.Find("tlp_DivisionGrid", false)[0]);
DivisionModulesList dml;
foreach (LayoutDivision ld in _LayoutDivisions)
{
dml = new DivisionModulesList(ld);
dml.BoundDivision = ld;
tlp.Controls.Add(dml);
}
}
private void Tlp_DivisionGrid_Paint(object sender, PaintEventArgs e)
{
}
}
}
When creating your own Properties for a UserControl, and you use this UserControl at another place, the Designer is generating Code for this property like:
yourControl.BoundLayout = null;
Search for it in the Designer.cs file; it will solve the problem until the code is regenerated.
If the designer displays your control it runs your code, and displays your MessageBox at Design-Time (not Build or Runtime).
Do avoid this forever put
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), Browsable(false)]
public Layout BoundLayout
on all your properties, if you intend to modify it by code only and not within the designer, especially if null is an invalid value.
When using your UserControl again at another place it will not create this BoundLayout=null again any more, but for existing references to your UserControl, you have to remove this line manually.
General Advice: In general, you should throw an exception rather than showing a MessageBox. But it has nothing to do with the problem.
You have defined the initial value of the property as null. This means, when you drop an instance of the control on the form, it will serialize the null assignment as well and generates a code like this:
userControl1.Name = "userControl1";
userControl1.Size = new Size( 100, 100);
userControl1.SomeProperty = null;
...
To solve the problem, you can use either of the following options:
Prevent designer from serializing the value if it's null.
Disable the validation at design time.
Prevent designer from serializing the value always. (as also proposed by Holger)
Example 1 - Prevent designer from serializing the value if it's null
You can set the default value of the property as null using DefaultValue attribute. Then it will not be serialized by designer when the value of the property is null when you drop the control on the form or when assign null value to the property at design time.
private SomeType someProperty = null;
[DefaultValue(null)]
public SomeType SomeProperty
{
get { return someProperty; }
set
{
if (value == null)
MessageBox.Show("Why null????");
else
someProperty = value;
}
}
Example 2 - Disable the validation at design time
You can check if the control is in DesignMode then stop validation:
private SomeType someProperty = null;
public SomeType SomeProperty
{
get { return someProperty; }
set
{
if (value == null && !DesignMode)
MessageBox.Show("Why null????");
else
someProperty = value;
}
}
I have a WPF control that is supposed to be simple to (re)use. For that I have a custom type containing all the settings the control is supposed to represent and bind it over a DependencyProperty.
However, whenever I change one of the members in the control, the parent control gets the changes in the member (when evaluated through other means), but the PropertyChanged-Callback never gets triggered in the parent control.
public class Setting
{
public int Prop {get;set;}
//Other Properties, Constructor & Copy Constructor, etc.
public override bool Equals(object obj)
{
if (!(obj is Setting other)) return false;
return Prop == other.Prop;
}
}
public class SettingControl : UserControl, INotifyPropertyChanged
{
public static readonly DependencyProperty SettingProperty = DependencyProperty.Register
(nameof(Settings), typeof(Setting), typeof(SettingControl),
new PropertyMetadata(default(Setting), OnValuePropertyChanged));
public Setting Settings
{
get => (Setting)GetValue(SettingProperty);
set
{
SetValue(SettingProperty, value);
OnPropertyChanged(nameof(Settings));
}
}
public int Prop
{
get => ((Setting)GetValue(SettingProperty))?.Prop ?? 0;
set
{
//Does not work:
var temp = (Setting)GetValue(SettingProperty);
temp.Prop = value;
Settings = temp;
OnPropertyChanged(nameof(Prop));
//Does not work:
Settings.Prop = value;
OnPropertyChanged(nameof(Prop));
OnPropertyChanged(nameof(Settings));
//**Does work**, and triggers the OnSettingChanged in the parent control,
//but is simply not great memory usage
Settings = new Setting(Settings){ Prop = value };
OnPropertyChanged(nameof(Prop));
}
}
}
//Relevant snippet from parent Control ViewModel:
public static readonly DependencyProperty SettingProperty =
DependencyProperty.Register(nameof(Settings), typeof(Setting), typeof(ControlViewModel),
new PropertyMetadata(default(Setting), (d, e) => ((ControlViewModel)d).OnSettingChanged()));
//OnSettingChanged() is never called
public Setting Settings
{
get => (Setting)GetValue(SettingProperty);
set //Set is never called when the member properties are changed
{
SetValue(SettingProperty, value);
OnPropertyChanged(nameof(Settings));
}
}
//Relevant snippet from parent xaml:
<local:SettingControl Width="300"
Settings="{Binding Path=Settings, Mode=TwoWay}"/>
// UpdateSourceTrigger=PropertyChanged doesn't help here either
An obvious solution of course would be to either wrap the Setting class into a SettingViewModel, or implement it as a ViewModel itself (small testing didn't show results anyway). This however would make the usage of the control a lot harder, and to some degree break MVVM (more than this already). There are also some XML things in the Setting class for serialization that I don't want to mess with.
One thing I noticed is that if the Equals function in Setting is coded to always return true the two ways of setting the member property that normally don't work, suddenly work and trigger the desired behavior.
Thanks in Advance.
I often have a situation like this when creating simple data objects. I have a property called Label that should have a default based on the Name of the object. So if no label is set then the Name is used otherwise use the set Label. A simple example in C#
public class FooBat {
public string Name { get; set; }
public string Label {
get {
if (_label == null) return Name;
return _label;
}
set { _label = value; }
}
}
Now the problem is if you want to edit this object you can't just bind to the Label property or you will get the default value and it will look as if there is a value there when there really isn't. So what I end up doing is create another, read-only property that does the defaulting and I use that is all instances except for when the base object is being edited. This leads to many extra properties with weird names like LabelWithDefault. Another alternative I've tried is to make Label handle the defaulting and make a new property called RealLabel that is used for editing the base object. This is just as bad.
I've thought of moving the defaulting code somewhere else but I haven't found a good place for it in any "normal" model that does not replicate the defaulting code many times.
What I have started to do now is initialize the Label field when the Name field is set (and the Label field is not) and then treat the Label field as a normal field. This works but now the code for defaulting is tied to the wrong property. Why should the Name know that the Label field cares about it? So this is also not "right."
Does anyone have any better ways of handling this problem?
I think there is a little confusion about what I'm asking for. Basically I need two different views to the same object for two different uses. In the first is the editing of the object itself where I want unset fields to show as empty (unset). The second is for all other cases (including when the object is the value of a field of another object) where I want to show each field with its dynamically determined default. Just setting the default the first time doesn't no help because if the (in this case) Name field changes then the Label field must also change until the Label field is set.
The answers are getting closer but I still think that they are too targeted to the example I gave. I was trying to give a concrete example for expository purposes but in reality this is more of a best-practices issue. The example I gave was C# and for a string property but I have the same problem with most languages and systems that I use that have frameworks where the data access and data display are handled for you as well as for data types other than strings. Changing the object that is queried from the data source is possible but often tricky and knowing when to make the change (use a sublclass in this case but not in that one) is particularly difficult.
public class FooBat {
public string Name { get; set; }
public string Label {
get {
if (_label == null)
_label = Name;
return _label;
}
set { _label = value; }
}
}
Regarding your update:
You could subclass your object. The base-class would return null if the field has not been set and the sub-class would return your default value. Thus if you need to query if a value has been set, you would cast to the base-class.
Deleted previous answers/updates for brevity.
Update 2:
I would have to say the best way is to track whether the property has been set or not with an IsPropertySet bool. The Getter for the property would check that value to see if it should be returning its own value or the default value. And the setter for the property would set the IsPropertySet according to the set value (true if the value is not null, false if it is). The code that is using the class could then look at the IsPropertySet value to determine if it is receiving a set value or the default when it calls the Property's Getter.
public class FooBat {
public string Name { get; set; }
public bool IsLabelSet { get; set; }
public string Label {
get {
if (IsLabelSet)
return _label;
else
return Name;
}
set {
IsLabelSet = value != null;
_label = value;
}
}
}
I use a Nameable interface a lot (with getName()). Before I start, I'll suggest that you don't want to do this at all. It should be the domain of your display logic, not your domain objects. Usually it's the code consuming the FooBat that is able to make this decision in a better way than the object itself. That aside...
public interface Label{
string getLabel();
boolean isDefault(); //or isValued() or use instanceof expressions
}
public interface Nameable{
string getName();
}
public class FooBat implements Nameable {
public string Name { get; set; }
public Label Label {
get {
if (_label == null) {
_label = new DefaultLabel(this);
}
return _label;
}
set { _label = value; }
}
}
public class DefaultLabel implements Label{
public DefaultCharSequence(Nameable named){
this.named = named;
}
public string getLabel(){
return named.getName();
}
public boolean isDefault(){ return true; }
}
public class StringLabel implements Label {
...
}
It all essentially boils down to returning a better class for your label object.
I want to create a method that changes enabled property. How do I pass the contorl name and property to a method.
If the following were my original method:
public void ChangeProperties()
{
btnAcesScore.Enabled = true;
}
I want to be able to change the "btnAcesScore" each time I call this method. How do I pass this to the method. I tried passing it as a string but that doesn't work.
Here is what I tried:
public void ChangeProperties(string category)
{
category = true;
}
ChangeProperties("btnAcesScore.Enabled");
Susan
Try this :
public void ChangeProperties(Control ctrl)
{
ctrl.Enabled = true;
}
and call it like that :
ChangeProperties(btnAcesScore);
What exactly is the purpose of this? Is it to reuse the method to arbitrarily change the Enabled property of any given control? If so, there is an easier way to accomplish it, as outlined by Canavar.
Or is the point of this method to toggle the setting? In which case, your method would look either like:
public void ChangeProperties()
{
btnAcesScore.Enabled = !btnAcesScore.Enabled;
}
or
public void ChangeProperties(Control ctrl)
{
ctrl.Enabled = !ctrl.Enabled;
}
depending on whether you wanted to hit just the one control, or provide access to many. In any event, I personally don't see much point to encapsulating a single property access within a method, and if you were insistent (and this method didn't adjust other properties), I'd at least rename it to something like ToggleEnabled.
Since the original question had a reflection tag I think she wanted a reflection answer (whether or not that is good design) so here is a Reflection answer.
the form has a controls collection and with this you can search for it and use reflection to set the property:
public void ChangeProperties(Form form, string category)
{
string[] parts = category.Split(".");
int index = form.Controls.IndexOfKey(parts[0]);
Control control = null;
if (index >= 0)
{
control = form.Controls[index].;
}
if (control != null)
{
PropertyInfo propertyInfo = control.GetType().GetProperty(parts[1]);
if (propertyInfo != null)
{
propertyInfo.SetValue(control, true);
}
}
}
if you call it from the form the control lives on
ChangeProperties(this, "btnAcesScore.Enabled");
How about also
void ChangeProperty(ref bool output)
{
output = true;
}
ChangeProperty(ref btnAcesScore.Enabled);
Not sure I totally understand your intent, but you could pass a delegate to some code that changed your property...
public void ChangeProperties(Action<bool> setprop)
{
...
setprop(true);
}
then call it:
ChangeProperties(b => btnAcesScore.Enabled = b);
I'd use reflection - use the GetType() Method on the object you send through to your method and then use the GetProperties to match against the property you send through. You can then set the values at that point.
Try this:
public void ChangeProperties(string category, object value)
{
var categoryConcat = category.Split('.');
var control = this.Controls.Cast<Control>()
.Where(x => x.Name == categoryConcat[0]).First();
control.GetType().GetProperty(categoryConcat[1])
.SetValue(control, value);
}
The example probably needs some checks on the existance of the control and the property.
Main()
{
ChangeProperties(ref category,True); //Where Category is the ID of the Textbox control i.e <asp:textbox ID="Category "></textbox>
}
public void ChangeProperties(ref TextBox category,bool val)
{
category.Enabled = val;
}