CODEWITHSUNDEEP
wpfdata-bindingbinding
PrimeTSS
PrimeTSS

Reputation: 2713

WPF Binding to local variable

Can you bind to a local variable like this?

SystemDataBase.cs

namespace WebWalker
{
    public partial class SystemDataBase : Window
    {
        private string text = "testing";
...

SystemDataBase.xaml

 <TextBox 
       Name="stbSQLConnectionString" 
       Text="{SystemDataBase.text}">
 </TextBox>

??

Text is set to the local variable "text"

Upvotes: 30

Views: 107780

Answers (5)

A-Sharabiani
A-Sharabiani

Reputation: 19329

Need to add the following line in the int constructor:

this.DataContext = this;

And use this in the XAML:

<TextBox Text = "{Binding SomeProperty}" />

Exmaple:

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public string PersonName { get; set; }

    public MainWindow()
    {
        InitializeComponent();            
        PersonName = "default";
        this.DataContext = this;
    }

    void button1_Click(object sender, RoutedEventArgs args)
    {            
        MessageBox.Show($"Hello {PersonName}");
    }
}

MainWindow.xaml

<StackPanel>
        <TextBox Name="textbox1" 
                 Text="{Binding PersonName, Mode=TwoWay}"
                 />
        <Button Name="button1" Click="button1_Click" Content="Click Me" />
</StackPanel>

Upvotes: 1

Danny Varod
Danny Varod

Reputation: 18068

To bind to a local "variable" the variable should be:

  1. A property, not a field.
  2. Public.
  3. Either a notifying property (suitable for model classes) or a dependency property (sutable for view classes)

Notifying property example:

public MyClass : INotifyPropertyChanged
{
    private void PropertyType myField;

    public PropertyType MyProperty
    {
        get
        {
            return this.myField;
        }
        set
        {
            if (value != this.myField)
            {
                this.myField = value;
                NotifyPropertyChanged("MyProperty");
            }
        }
    }

    protected void NotifyPropertyChanged(String propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

Dependency property example:

public MyClass : DependencyObject
{
    public PropertyType MyProperty
    {
        get
        {
            return (PropertyType)GetValue("MyProperty");
        }
        set
        {
            SetValue("MyProperty", value);
        }
    }

    // Look up DependencyProperty in MSDN for details
    public static DependencyProperty MyPropertyProperty = DependencyProperty.Register( ... );
}

Upvotes: 30

user1228
user1228

Reputation:

The pattern is:

public string Text {get;set;}

and the binding is 

{Binding Text, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}

If you want the binding to update automatically you should make it a DependencyProperty.

I think 3.5 added ElementName to bindings, so the following is a little easier:

<Window x:Name="Derp" ...
  <TextBlock Text="{Binding Text, ElementName=Derp}"/>

Upvotes: 42

AnjumSKhan
AnjumSKhan

Reputation: 9827

To bind a local variable which is present in your Window class it has to be : 1. Public property 2. A notifying property. For this your window class should implement INotifyPropertyChanged interface for this property.

Then in the constructor

public Assgn5()
{           
    InitializeComponent();

    this.DataContext = this; // or **stbSQLConnectionString**.DataContext = this;
}

 <TextBox 
   Name="stbSQLConnectionString" 
   Text="{Binding text}">
 </TextBox>

Upvotes: 3

Neil
Neil

Reputation: 4049

If you're doing a lot of this, you could consider binding the DataContext of the whole window to your class. This will be inherited by default, but can still be overridden as usual

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}">

Then for an individual components you can use

Text="{Binding Text}"

Upvotes: 21

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