c# - 为 Window1 中 ViewModel 的 TextBlock.Text 赋值，并将 TextBlock.Text 的值用于 Window2

问题描述

我遇到了 MVVM 和 WPF 应用程序的一个特殊问题。我将简要解释一下，以使其尽可能清楚。

首先，我在 XAML 文件中绑定了 TextBlock 属性的文本

XAML

<TextBlock
    x:Name="ProjectCredentials"
    Text="{Binding Path=HeaderName}"/>

查看模型 - 在 MainWindow 中创建

namespace Test
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

    public class MainWindowViewModel : INotifyPropertyChanged
    {
        private string _tabitemHeader;
        public string HeaderName
        {
            get
            {   
                return _tabitemHeader;
            }
            set
            {
                _tabitemHeader = value;
                OnPropertyChanged("HeaderName");
            }
        }
    }
    // Continue in next code block
}

下面是我想为我的 TextBlock.Text 属性赋予价值的LoginScreen 窗口或窗口 1。

namespace Test
{
    public partial class LoginScreen : Window
    {
        public LoginScreen()
        {
            InitializeComponent();
        }

        private void LoginButton_Click(object sender, RoutedEventArgs e)
        {
            MainWindow win2 = new MainWindow();

            win2.DataContext = new MainWindow.MainWindowViewModel();

            MainWindow.MainWindowViewModel object_change = win2.DataContext as MainWindow.MainWindowViewModel;

            object_change.HeaderName = "Project Name: " + SQLSeverName.Text + " - " + SQLDatabasesComboBox.SelectedItem;
            Debug.WriteLine(object_change.HeaderName);
            //Successfully returns the string
        }
    }
}

现在我已经给出了值，"Project Name: ..."我应该在方法内的 MainWindow 中调用这个字符串GetHeaderDetails()

namespace Test
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

    public class MainWindowViewModel : INotifyPropertyChanged
    {
        private string _tabitemHeader;
        public string HeaderName
        {
            get
            {   
                return _tabitemHeader;
            }
            set
            {
                _tabitemHeader = value;
                OnPropertyChanged("HeaderName");
            }
        }
    }
    public List<string> GetHeaderDetails()
    {
        string projectdetails_option1 = ?.HeaderName; //how can  I call the HeaderName of MainWindow DataContext which is already filled from LoginScreen window?

        Debug.Assert(projectdetails_option1 != null, "Project name not found!"); //this returns null

        string connectiondetails = projectdetails_option1.Split(": ")[1];

        string servernamedetails = connectiondetails.Split(" - ")[0].Trim();
        string projectnamedetails = connectiondetails.Split(" - ")[1].Trim();

        List<string> connectiondetailslist = new List<string>();
        connectiondetailslist.Add(servernamedetails);
        connectiondetailslist.Add(projectnamedetails);

        return connectiondetailslist;
    }

    public List<string> ConnectionDetailsList { get => GetHeaderDetails(); set => ConnectionDetailsList = value; }
}

这里的问题是如何调用已经从 LoginScreen 窗口填充的 MainWindow DataContext 的 HeaderName？

我知道，如果我在 GetHeaderDetails() 方法中打开 MainWindow DataContext 的一个新实例，我将得到一个 NullReferenceException，因为 HeaderName 将丢失并且将引入一个新的 DataContext。所以我想找到一种方法来绕过这个。

请注意，我知道NullReferenceException。虽然，我正在寻找可以帮助我理解如何定位问题的答案。

问候。

标签： c#wpfmvvm

I have figured it out, finally. To retrieve the value of the TextBlock.Text value in MainWindow, the only thing that I had to do is:

Instead of this:

string projectdetails_option1 = ?.HeaderName;

I tried this:

string projectdetails_option1 = ProjectCredentials.Text; //The TextBlock that got its value from LoginScreen.

And successfully I retrieved the value of the ProjectCredentials textblock, without opening a new instance of the DataContext.

c# - 为 Window1 中 ViewModel 的 TextBlock.Text 赋值，并将 TextBlock.Text 的值用于 Window2

问题描述

解决方案

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