Question

I add code in .cs

 public static readonly DependencyProperty lbStatusProperty =
        DependencyProperty.Register("lbStatus", typeof(string), typeof(SingleTalkView),
        new PropertyMetadata(""));

    public string lbStatus
    {
        get { return (string)GetValue(lbStatusProperty); }
        set { SetValue(lbStatusProperty, value); }
    }

in xaml

<TextBlock Text="{Binding lbStatus}" Style="{StaticResource PhoneTextNormalStyle}" Height="24"/>

And then add a global value

private string a = "Test";

and in init function

this.lbStatus = a;

Finally I add a button and change a’s value,the TextBlock doesn’t change!why?
Thx~~~~

Answer 1

String, in .NET, is an immutable type. When you type:

this.lbStatus = a;

You set lbStatus to a reference to the string currently pointed to by the a variable. Later, when you change a:

a = "Foo";

You’re not going to change this.lbStatus, since you’re assigning the a variable to a completely new string instance.