如何在运行时将值从窗口传递给用户控件？

Question

This is my user control code behind where I should get the data:

This is my main window where I included the user control and set the value to the property:

This doesn't work as the value is always null. Please help to correct anything that I've done wrong. Thanks.

Answer 1

It looks like you need to use a dependency property as far as I know. This will replace the GetMyValue property you have.

check out this example for custom dependency properties.

https://www.tutorialspoint.com/wpf/wpf_dependency_properties.htm

Side Note: a quick way to make one is to type "propdp" and then tab twice. Then tab your way through setting it up.

Answer 2

1.Make sure you had set the Scope on 'User' rather than 'Admin', otherwise you won't have writing access to Recourses. 2.Make sure you have saving method after modifying data.

For writing using Properties.Settings;

Settings.Default.myProperty = myValue;
Settings.Default.Save();

For Reading

String myValue = Settings.Default["myProperty"].ToString();

You can also manage your properties from Solution Explore > Your Project > Properties > Settings.settings

Answer 3

One good solution for doing this:

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    var control = new UserControl1();
    control.GetMyValue = "HelloWorld";
    grid1.Childern.Add(control);
}

There are other solutions, like Binding DataContext or making a custom DependencyProperty

Answer 4

The UserControl is created before the GetMyValue property is set. You cannot set a property of an instance before you have created it...

Wait until the UserControl has been loaded and you will get the value as expected:

public UserControl1()
{
    InitializeComponent();
    Loaded += (s, e) =>
    {
        string finalValue = GetMyValue;
    };
}

Answer 5

You need to create Dependency property. There's no hard to do:

First you need to register:

public static readonly DependencyProperty GetMyValueProperty =
            DependencyProperty.Register("GetMyValue", typeof(string), 
            typeof(UserControl1), new UIPropertyMetadata(string.Empty));  

Then create auto-property:

public string GetMyValue
        {
            get { return (string )GetValue(GetMyValueProperty ); }
            set { SetValue(GetMyValueProperty , value); }
        }

That's all, just copy this examples into your UserControl1 class.