请帮助将参数传递给父页面 [英] Please help passing parameter to parent page

问题描述

我有子页面：

i have child page :

public partial class display1 : Page
    {
        private Page3 mdiParent;
        public display1()
        {
            InitializeComponent();
        }

        public display1(Page3 m1_)
        {
            InitializeComponent();
            this.mdiParent = m1_;
        }

        private void btnFin_Click(object sender, RoutedEventArgs e)
        {
            this.mdiParent.ChildMessage = "TEST";  // error here,Object reference not set to an instance of an object.
            this.mdiParent.UpdateMessage();
        }
    }

i需要将参数传递给父页面：

i need to pass parameter to parent page here :

public partial class Page3 : Page
    {
        public Page3()
        {
            InitializeComponent();
        }

        private string childMessage;
        public string ChildMessage
        {
            get { return childMessage; }
            set { childMessage = value; }
        }

        private void btnDisplay_Click_1(object sender, RoutedEventArgs e)
        {
            framediag.Navigate(new display1());
        }

        public void UpdateMessage()
        {
            textBox1.Text = ChildMessage;
        }

        public void UpdateMessage(string message)
        {
            textBox1.Text = message;
        }

请帮忙，明天我必须完成这项工作

please help, i have to done this work tomorrow

推荐答案

在您的子类中，您有以下两个构造函数：

In your child class you have the following two constructors:

public display1()
{
    InitializeComponent();
}

public display1(Page3 m1_)
{
    InitializeComponent();
    this.mdiParent = m1_;
}

在您的父类中，您可以调用不带参数的那个：

In your parent class you call the one without parameters:

private void btnDisplay_Click_1(object sender, RoutedEventArgs e)
{
    framediag.Navigate(new display1());
}

因此从未设置 mdiParent 变量，导致错误看到。您需要在构造函数的第二个版本中传递对父项的引用，例如：

So the mdiParent variable is never set, leading to the error you see. You need to pass a reference to the parent in the second version of the constructor, something like:

private void btnDisplay_Click_1(object sender, RoutedEventArgs e)
{
    framediag.Navigate(new display1(this));
}

谢谢Richard MacCutchan先生：）

Thank you Mr. Richard MacCutchan :)

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