In my application, I will need to update a certain image when the selection of my combobox changes. Currently I do this by capturing the SelectedIndexChanged event and update the image there.
I have been trying another approach to do it, namely, using Binding in order to simplify my code, but it doesn't work.
Because the binding of ComboBox.SelectedItem to a certain property only applies after the ComboBox loses focus or when another control gains focus-- not when or before the SelectedIndexChanged event is fired.
How to get the binding to apply immediately when the SelectedItem or the SelectedIndex is changed?
This is my code:
public partial class Form1 : Form
{
private readonly Person person;
public Form1()
{
InitializeComponent();
person = new Person()
{
Name = "joe",
Race = Race.Indian
};
textBox1.DataBindings.Clear();
textBox1.DataBindings.Add(nameof(textBox1.Text), person, nameof(person.Name));
comboBox1.DataSource = Enum.GetValues(typeof(Race));
comboBox1.DataBindings.Clear();
comboBox1.DataBindings.Add(nameof(comboBox1.SelectedItem), person, nameof(person.Race));
comboBox1.SelectedIndexChanged += ComboBox1_SelectedIndexChanged;
}
private void ComboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
//when selected index is changed, the data is lagging behind the selected item.
//eg: SelectedItem is already Chinese, but person.Race is still Indian
MessageBox.Show($"data {person.Race}, selected item {comboBox1.SelectedItem}");
}
private int count = 0;
private void button1_Click(object sender, EventArgs e)
{
person.Race =(Race)(((int)person.Race + 1) % Enum.GetValues(typeof(Race)).Length);
person.Name = person.Name + $"{count++}";
}
}
public enum Race
{
Indian,
Chinese,
Causacian,
Arabian,
Jewish,
SouthINdian,
}
public class Person: INotifyPropertyChanged
{
private Race _race;
private string _name;
public string Name
{
get
{
return _name;
}
set
{
_name = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Name)));
}
}
public Race Race
{
get
{
return _race;
}
set
{
_race = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs (nameof(Race)));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
To solve the problem, you can bind to SelectedValue property:
comboBox1.DataSource = Enum.GetValues(typeof(Race)).Cast<Race>()
.Select(x => new { Value = x, Display = x.ToString() })
.ToList();
comboBox1.DisplayMember = "Display";
comboBox1.ValueMember = "Value";
comboBox1.DataBindings.Add(nameof(comboBox1.SelectedValue), person, nameof(person.Race),
true, DataSourceUpdateMode.OnPropertyChanged);
Related
I'm trying a code which changes the TextBox values when variable mapped with it changes accordingly without using TextBox changed event. I am not finding any clue to where to start please help me.
Here is the code:
public void varChange(TextBox text)
{
String name;
name="sachin";
text.Text = name;
MessageBox.Show("" + text.Text);
}
You can "extend" TextBox :
public class MeTextBox : TextBox
{
public override string Text
{
get
{
return base.Text;
}
set
{
//base.Text = value; // use it or not .. whatever
MyTextWasChanged();
}
}
void MyTextWasChanged()
{
String name;
name="sachin";
//text.Text = name;
base.Text = name;
MessageBox.Show("" + text.Text);
}
}
If that's not what you're looking for then give some more details and I'll update this answer.
You can use a BindingSource
public partial class Form1 : Form
{
private System.Windows.Forms.BindingSource form1BindingSource;
public string BindedProp { get; set; } //Variable or property binded with TextBox
public Form1()
{
InitializeComponent();
this.form1BindingSource = new System.Windows.Forms.BindingSource(new System.ComponentModel.Container());
this.form1BindingSource.DataSource = typeof(binding.Form1);
this.textBox.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.form1BindingSource, "BindedProp", true));
this.form1BindingSource.DataSource = this;
}
//add a button control to assing value code event click
private void btAssingValueProperty_Click(object sender, EventArgs e)
{
BindedProp = "Value assigned";
form1BindingSource.ResetBindings(false);
}
//add a other button control to show value code event click
private void btShowValueProperty_Click(object sender, EventArgs e)
{
MessageBox.Show(BindedProp);
}
}
I am binding ListCollectionView to BindingSource which in turn is binded to DataGridView (winforms). But Whenever new object is added to ListCollectionView BindingSource is not getting updated automatically. I need to make it NULL and re-bind again.
//Binding to Datagrid
bindingProvider.DataSource = this.GetController.ProvidersView;
this.dgvProviders.DataSource = bindingProvider;
After that in Add Button Click.
//Adds new object in ProvidersView Collection.
this.GetController.AddEditProvider();
this.bindingProvider.DataSource = null;
this.bindingProvider.DataSource = this.GetController.ProvidersView;
Can someone please let me know the easy way of refreshing the Bindingsource.
Below is the sample code
BindingList<DemoCustomer> lstCust = new BindingList<DemoCustomer>();
BindingListCollectionView view;
private void Form1_Load(object sender, EventArgs e)
{
lstCust.Add(DemoCustomer.CreateNewCustomer());
lstCust.Add(DemoCustomer.CreateNewCustomer());
lstCust.Add(DemoCustomer.CreateNewCustomer());
lstCust.Add(DemoCustomer.CreateNewCustomer());
view = new BindingListCollectionView(lstCust);
bindingSource1.DataSource = view;
dataGridView1.DataSource = bindingSource1;
}
private void button1_Click(object sender, EventArgs e)
{
this.lstCust.Add(DemoCustomer.CreateNewCustomer());
bindingSource1.EndEdit();
this.bindingSource1.ResetBindings(false);
//(bindingSource1.DataSource as BindingListCollectionView).NeedsRefresh
dataGridView1.Refresh();
}
public class DemoCustomer : INotifyPropertyChanged
{
// These fields hold the values for the public properties.
private Guid idValue = Guid.NewGuid();
private string customerNameValue = String.Empty;
private string phoneNumberValue = String.Empty;
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(string propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
// The constructor is private to enforce the factory pattern.
private DemoCustomer()
{
customerNameValue = "Customer";
phoneNumberValue = "(312)555-0100";
}
// This is the public factory method.
public static DemoCustomer CreateNewCustomer()
{
return new DemoCustomer();
}
// This property represents an ID, suitable
// for use as a primary key in a database.
public Guid ID
{
get
{
return this.idValue;
}
}
public string CustomerName
{
get
{
return this.customerNameValue;
}
set
{
if (value != this.customerNameValue)
{
this.customerNameValue = value;
NotifyPropertyChanged("CustomerName");
}
}
}
public string PhoneNumber
{
get
{
return this.phoneNumberValue;
}
set
{
if (value != this.phoneNumberValue)
{
this.phoneNumberValue = value;
NotifyPropertyChanged("PhoneNumber");
}
}
}
}
Please let me know whats the issue with my code. Whenever I add any new item its not reflected in BindingSource bcoz of tht its not reflecting in DataGridView
www.techknackblogs.com
Make sure your underlying collection (that you used to create the CollectionView) implements INotifyCollectionChanged.
For example, instead of using a List<T>, use ObservableCollection<T> or BindingList<T>.
This allows changes to the collection (adding an element) to propagate to the CollectionView.
I read some about DataBinding, mostly complicated things like SQL or whatever XAML and stuff.
All I want my programm to do is, if the "value" of a variable changes just write it in a textbox or label. (using WindowsForms)
So far what I have:
namespace DataBinding_Test
{
public partial class Form1 : Form
{
BindingSource bs = new BindingSource();
Class1 test = new Class1();
public Form1()
{
InitializeComponent();
test.name = "Hello";
bs.DataSource = test;
label1.DataBindings.Add(new Binding("Text", bs, "name", false, DataSourceUpdateMode.OnPropertyChanged));
}
private void button1_Click(object sender, EventArgs e)
{
test.name = textBox1.Text;
}
}
}
Class1 just has a public property name. On startup lable1 will show my "Hello" string. Then on button click the name property will change. On debug I saw the actual DataSource of "bs" contains the new property value, but the label will not show anything...
Is there any realtivly easy way to do this?
The Backround is: periodically there will be a polling of sensor data throug RS232. If the value of one sensor changes I want to show this in label or textbox. Now a backroundthreaded timer will need invokes and stuff to access the GUI thread; thought this would be easier with databinding but seems not :P
Thanks to all, great site, great work! :)
Another way to make things work without implementing INotifyPropertyChanged
class Class1
{
private string name;
public string Name
{
get { return name; }
set
{
//Check if you are assigning the same value. Depends on your business logic
//here is the simplest check
if (Equals(name, value))
return;
name = value;
OnNameChanged();
}
public event EventHandler NameChanged;
protected virtual void OnNameChanged()
{
var handler = NameChanged;
if (handler != null)
handler(this, EventArgs.Empty);
}
}
}
The trick is to have event with the name combined by name of property and Changed suffix and to raise it whenever value of your property is changed
In order your code would work you should implement INotifyPropertyChanged interface in your binded class. Without it your binding simply doesn't know, when the change occures. There you should implenent the logic, according to which you would notify your subscribers about which when something changed in your class (the setter part) and what has changed (PropertyChangedEventArgs). See example for your class:
class Class1: INotifyPropertyChanged
{
private string name = "";
public string Name
{
get { return name; }
set { name = value; NotifyPropertyChanged(); }
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged()
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Name"));
}
}
}
And change the property name from "name" to "Name" in your binding:
label1.DataBindings.Add(new Binding("Text", bs, "Name", false, DataSourceUpdateMode.OnPropertyChanged));
// create winforms project on form1 drag a textbox (testbox1)
// and a button (button1) with a button click event handler
// this updates the textbox when the button is clicked
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace WindowsFormsApplication3
{
public partial class Form1 : Form
{
MyClass Myobj = new MyClass();
public Form1()
{
InitializeComponent();
/* propertyname, datasource, datamember */
textBox1.DataBindings.Add("Text", Myobj, "Unit");
}
public class MyClass : INotifyPropertyChanged
{
private int unit = 3;
/* property change event */
public event PropertyChangedEventHandler PropertyChanged;
public int Unit
{
get
{
return this.unit;
}
set
{
if (value != this.unit)
{
this.unit = value;
NotifyPropertyChanged("Unit");
}
}
}
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
private void button1_Click(object sender, EventArgs e)
{
Myobj.Unit += 4;
}
}
}
I created an extension method for this that I would like to share
Usage
private void Form1_Load(object sender, EventArgs e)
{
ResultLabel.Bind(NameTextBox);
WarningLabel.Bind(NameTextBox,i => i.Length == 0 ? "field required!" : "");
SendButton.Bind(NameTextBox, i => SendButton.Enabled = !(i.Length == 0));
}
Extension
public static class Extention
{
public static void Bind(this Control owner, Control dataSource)
{
List<EventInfo> fields = dataSource.GetType().GetEvents().ToList();
int index = fields.FindIndex(item => item.Name == "TextChanged");
if (index >= 0)
{
Control sender = dataSource as Control;
owner.Text = dataSource.Text;
dataSource.TextChanged += delegate (Object o, EventArgs e) { owner.Text = sender.Text; };
}
}
public static void Bind(this Control owner, Control dataSource, Func<string,string> onChange)
{
List<EventInfo> fields = dataSource.GetType().GetEvents().ToList();
int index = fields.FindIndex(item => item.Name == "TextChanged");
if (index >= 0)
{
Control sender = dataSource as Control;
owner.Text = onChange(sender.Text);
dataSource.TextChanged += delegate (Object o, EventArgs e) { owner.Text = onChange(sender.Text); };
}
}
public static void Bind(this Control owner, Control dataSource, Action<string> onChange)
{
List<EventInfo> fields = dataSource.GetType().GetEvents().ToList();
int index = fields.FindIndex(item => item.Name == "TextChanged");
if (index >= 0)
{
Control sender = dataSource as Control;
onChange(sender.Text);
dataSource.TextChanged += delegate (Object o, EventArgs e) { onChange(sender.Text); };
}
}
}
I'm not sure if that is what you want but you can can write whatever you variable contains into the Textbox or Label by using the control.Text property.
textBox1.Text ="Some other Text"
or
string variable = "Hello 2";
textBox1.Text = variable;
Why dou you want to use Databinding? Its mutch easier this way.
I have a Windows Forms ListBox data-bound to a BindingList of business objects. The ListBox's displayed property is a string representing the name of the business object. I have a TextBox that is not data-bound to the name property but instead is populated when the ListBox's selected index changes, and the TextBox, upon validation, sets the business object's name property and then uses BindingList.ResetItem to notify the BindingList's bound control (the ListBox) to update itself when the TextBox's text value is changed by the user.
This works great unless the name change is only a change in case (i.e. "name" to "Name"), in which case the ListBox doesn't get updated (it still says "name", even though the value of the underlying business object's name property is "Name").
Can anyone explain why this is happening and what I should do instead? My current workaround is to use BindingList.ResetBindings, which could work for me but may not be acceptable for larger datasets.
Update 9/27/2011: Added a simple code example that reproduces the issue for me. This is using INotifyPropertyChanged and binding the textbox to the binding list. Based on How do I make a ListBox refresh its item text?
using System;
using System.ComponentModel;
using System.Windows.Forms;
namespace WinformsDataBindingListBoxTextBoxTest
{
public partial class Form1 : Form
{
private BindingList<Employee> _employees;
private ListBox lstEmployees;
private TextBox txtId;
private TextBox txtName;
private Button btnRemove;
public Form1()
{
InitializeComponent();
FlowLayoutPanel layout = new FlowLayoutPanel();
layout.Dock = DockStyle.Fill;
Controls.Add(layout);
lstEmployees = new ListBox();
layout.Controls.Add(lstEmployees);
txtId = new TextBox();
layout.Controls.Add(txtId);
txtName = new TextBox();
layout.Controls.Add(txtName);
btnRemove = new Button();
btnRemove.Click += btnRemove_Click;
btnRemove.Text = "Remove";
layout.Controls.Add(btnRemove);
Load += new EventHandler(Form1_Load);
}
private void Form1_Load(object sender, EventArgs e)
{
_employees = new BindingList<Employee>();
for (int i = 0; i < 10; i++)
{
_employees.Add(new Employee() { Id = i, Name = "Employee " + i.ToString() });
}
lstEmployees.DisplayMember = "Name";
lstEmployees.DataSource = _employees;
txtId.DataBindings.Add("Text", _employees, "Id");
txtName.DataBindings.Add("Text", _employees, "Name");
}
private void btnRemove_Click(object sender, EventArgs e)
{
Employee selectedEmployee = (Employee)lstEmployees.SelectedItem;
if (selectedEmployee != null)
{
_employees.Remove(selectedEmployee);
}
}
}
public class Employee : INotifyPropertyChanged
{
private string name;
private int id;
public string Name
{
get { return name; }
set
{
name = value;
OnPropertyChanged("Name");
}
}
public int Id
{
get { return id; }
set
{
id = value;
OnPropertyChanged("Id");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
#endregion
}
}
Update 9/28/2011: The problem seems to be internal to the ListBox control, specifically the way it decides (not) to update an item if its string representation is equivalent to the new value, ignoring case differences. As far as I can tell this is hard coded into the control with no way to override it.
Think I found the problem:
I just hope this concept will be helpfull to solve your problem
I have a TextBox, the user input is compared to string "Name". My button click event is:
private void btn_Click(object sender, EventArgs e)
{
if(txt.Text == "Name")
MessageBox.Show("Value is Same");
}
If you write "name" in textbox, condition will be false. If you type type "Name" in textbox, condition will be true.
Now try changing the btn click:
using System.Globalization;
private void btn_Click(object sender, EventArgs e)
{
TextInfo ChangeCase = new CultureInfo("en-US", false).TextInfo;
string newText = ChangeCase.ToTitleCase(txt.Text);
if (newText == "Name")
MessageBox.Show("Value is Same");
}
now you type "name" or "Name" condition is true.
Remember it will just capaitalize the first letter of the string suplied. "my name" will outputted as "My Name".
And if your condition says:
if(txt.Text == "name")
MessageBox.Show(Value is Same);
Then you can try something like
string newText = (txt.Text).ToLower();
if(newText == "name")
MessageBox.Show(Value is Same);
Here the supplied string will outputted in the lower case always.
Hope it helps.
This really is the same problem as when renaming files or directories while only case is different. I suggest the same work-around that I found earlier:
if (oldValue.ToUpper() == newValue.ToUpper()){
ListBox1.Items[i] = newValue + "_tmp"; // only adding stuff to force an update
ListBox1.Items[i] = newValue; // now the new value is displayed, even only case has changed
}
Now for your question, I suggest you try to check if the setter is changing a value only in lower/upper case (a.ToUpper() == b.ToUpper()). If true, then first give a extra change, before the intended change, something like:
name = value + "_tmp";
OnPropertyChanged("Name");
name = value;
OnPropertyChanged("Name");
Hope this helps.
I created a simple example with data binding (unfortunately we have a similar case in our system). I created a funky combo box:
public class FunkyComboBox : ComboBox
{
private object currentValue = null;
public FunkyComboBox()
{
if (LicenseManager.UsageMode == LicenseUsageMode.Runtime)
this.Items.Add("Other...");
}
protected override void OnSelectedIndexChanged(EventArgs e)
{
if (!this.Text.StartsWith("Other") && currentValue != this.SelectedItem)
{
currentValue = this.SelectedItem;
BindingManagerBase bindingManager = DataManager;
base.OnSelectedIndexChanged(e);
}
}
protected override void OnSelectionChangeCommitted(EventArgs e)
{
string itemAsStr = this.SelectedItem != null ? SelectedItem.ToString() : "";
if (itemAsStr.StartsWith("Other"))
{
string newItem = "item" + this.Items.Count;
if (!Items.Contains(newItem))
{
Items.Add(newItem);
}
SelectedItem = newItem;
}
else
{
OnSelectedIndexChanged(e); //forces a selectedIndexChanged event to be thrown
base.OnSelectionChangeCommitted(e);
}
}
}
Which adds new items when you click Other (in our system it opens a form where you can query the database, etc). Then I have a simple data object:
public class MyClass
{
private string value;
public string MyData
{
get{ return value;}
set{ this.value = value;}
}
}
And a test form with two controls bound to this object (some designer code removed):
public partial class Form1 : Form
{
MyClass myObj = new MyClass();
public Form1()
{
InitializeComponent();
myObj.MyData = "Nothing";
myClassBindingSource.DataSource = myObj;
}
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.textBox1 = new System.Windows.Forms.TextBox();
this.myClassBindingSource = new System.Windows.Forms.BindingSource(this.components);
this.funkyComboBox1 = new DataBindingTests.FunkyComboBox();
((System.ComponentModel.ISupportInitialize)(this.myClassBindingSource)).BeginInit();
this.SuspendLayout();
//
// textBox1
//
this.textBox1.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.myClassBindingSource, "MyData", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged));
//
// myClassBindingSource
//
this.myClassBindingSource.DataSource = typeof(DataBindingTests.MyClass);
//
// funkyComboBox1
//
this.funkyComboBox1.DataBindings.Add(new System.Windows.Forms.Binding("SelectedItem", this.myClassBindingSource, "MyData", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged));
this.funkyComboBox1.DataBindings.Add(new System.Windows.Forms.Binding("SelectedValue", this.myClassBindingSource, "MyData", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged));
//
// Form1
//
this.Controls.Add(this.textBox1);
this.Controls.Add(this.funkyComboBox1);
((System.ComponentModel.ISupportInitialize)(this.myClassBindingSource)).EndInit();
this.ResumeLayout(false);
this.PerformLayout();
}
private FunkyComboBox funkyComboBox1;
private System.Windows.Forms.BindingSource myClassBindingSource;
private System.Windows.Forms.TextBox textBox1;
}
If you run this code and start playing with the combo box, you will notice that the edit box changes only if you click on it. After every change a null value is set to my object and the text box is cleared. How can I make it set the correct value after every change?
I'm not really sure why the ComboBox data binding behaves this way, but I have found a workaround. It seems as though the databinding doesn't work correctly if you don't use a datasource for your ComboBox's values.
I made a few minor changes to FunkyComboBox, and it now works as expected.
public class FunkyComboBox : ComboBox
{
private object currentValue = null;
private List<string> innerItems = new List<string>();
public FunkyComboBox()
{
if (LicenseManager.UsageMode == LicenseUsageMode.Runtime)
innerItems.Add("Other...");
this.DataSource = innerItems;
}
protected override void OnSelectedIndexChanged(EventArgs e)
{
if (!this.Text.StartsWith("Other") && currentValue != this.SelectedItem)
{
currentValue = this.SelectedItem;
BindingManagerBase bindingManager = DataManager;
base.OnSelectedIndexChanged(e);
}
}
protected override void OnSelectionChangeCommitted(EventArgs e)
{
string itemAsStr = this.SelectedItem != null ? SelectedItem.ToString() : "";
if (itemAsStr.StartsWith("Other"))
{
string newItem = "item" + this.Items.Count;
if(!innerItems.Contains(newItem))
{
innerItems.Add(newItem);
this.RefreshItems();
} SelectedItem = newItem;
}
else
{
OnSelectedIndexChanged(e);
//forces a selectedIndexChanged event to be thrown
base.OnSelectionChangeCommitted(e);
}
}
}
It seems to be a bug with the base ComboBox as well. It is not possible to get this binding source craziness to work correctly.