c# - ListView 仅显示空行。 WPF MVVM

Question

我正在尝试将 sqlite 数据表绑定(bind)到 ListView 。问题是它在数据库中显示正确的行数，但显示为空行。因此，如果数据计数为五，它会显示五个空数据行。下面是我的整个解决方案的代码。

using System;
using System.Collections.Generic;
using System.Linq;
using System.ComponentModel;
using System.Diagnostics;
using System.Globalization;
using System.Text.RegularExpressions;
using System.Data;
using System.Data.SQLite;
using WpfApplication_tutorial.Properties;

namespace WpfApplication_tutorial.Model
{
    public class Student : IDataErrorInfo
    {

        public Student(string firstName, string lastName)
        {
            this.FirstName = firstName;
            this.LastName = lastName;            
        }

        private Student() { }

        public string FirstName
        {
            get;
            set;
        }

        public string LastName
        {
            get;
            set;
        }

        string IDataErrorInfo.Error { get { return null; } }

        string IDataErrorInfo.this[string propertyName]
        {
            get { return this.GetValidationError(propertyName); }
        }

        public bool IsValid
        {
            get
            {
                foreach (string property in ValidatedProperties)
                    if (GetValidationError(property) != null)
                        return false;
                return true;
            }
        }

        static readonly string[] ValidatedProperties = 
       {
           "FirstName",
           "LastName"
       };

        string GetValidationError(string propertyName)
        {
            if (Array.IndexOf(ValidatedProperties, propertyName) < 0)
                return null;

            string error = null;

            switch (propertyName)
            {
                case "FirstName":
                    error = this.ValidateFirstName();
                    break;

                case "LastName":
                    error = this.ValidateLastName();
                    break;

                default:
                    Debug.Fail("Unknown property being validated on Student", propertyName);
                    break;
            }
            return error;
        }

        string ValidateFirstName()
        {
            if (IsStringMissing(this.FirstName))
            {
                return Strings.Student_MissingFirstName_Error;
            }
            return null;
        }

        string ValidateLastName()
        {
            if (IsStringMissing(this.LastName))
            {
                return Strings.Student_MissingLastName_Error;
            }
            return null;
        }

        static bool IsStringMissing(string value)
        {
            return
                String.IsNullOrEmpty(value) || value.Trim() == String.Empty;
        }
    }

}

下面是我的 View 模型的代码。它包括创建和从表中选择的功能

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Diagnostics;
using System.Threading;
using System.Security;
using System.Windows;
using System.Windows.Input;
using System.IO;
using System.Data;
using System.Data.SQLite;
using System.Windows.Media;
using System.Windows.Media.Animation;
using GalaSoft.MvvmLight;
using WpfApplication_tutorial.Model;
using WpfApplication_tutorial.View;
using WpfApplication_tutorial.UserControls;

namespace WpfApplication_tutorial.ViewModel
{
    public class StudentViewModel : ViewModelBase, IDataErrorInfo
    {
        readonly Student _student;
        private string firstName = string.Empty;
        private string lastName = string.Empty;
        private DataView studentDetails = null;


        // Command for registering new student
        private ICommand registerStudent;

        /// <summary>
        /// Initializes a new instance of the StudentViewModel class.
        /// </summary>
        public StudentViewModel()
        {
            _student = new Student(firstName, lastName);
            firstName = _student.FirstName;
            lastName = _student.LastName;
            FormOne();

        }

        public string FirstName
        {
            get { return _student.FirstName; }
            set
            {
                if (value == _student.FirstName)
                    return;
                _student.FirstName = value;
                OnPropertyChanged("FirstName");
            }
        }




///Please note that i tried this to
       public string FirstName
        {
           get { return firstNam; }
           set 
           { 
              firstName = value;
              OnPropertyChanged("FirstName");
           }
       }


        public string LastName
        {
            get { return _student.LastName; }
            set
            {
                if (value==_student.LastName)
                    return;
                _student.LastName = value;

                OnPropertyChanged("LastName");
            }
        }

        public DataView StudentDetails
        {
            get { return studentDetails; }
            set
            {
                if (value == studentDetails)
                    return;
                studentDetails = value;
                OnPropertyChanged("StudentDetails");
            }
        }


        public ICommand RegisterStudent
        {
            get
            {
                if (registerStudent == null)
                {
                    registerStudent = new CommandBase(i => this.CreateStudent(), null);
                }
                return registerStudent;
            }
        }

public void FormOne()
        {

            string databaseName = "Kwega.db3";
            SQLiteConnection connection = new SQLiteConnection("Data Source=" + databaseName + "; Version=3;");
            string students = "SELECT first_name, last_name FROM students";
            SQLiteDataAdapter adapter = new SQLiteDataAdapter(students, connection);
            connection.Open();
            adapter.SelectCommand.CommandTimeout = 120;
            DataSet ds = new DataSet();
            adapter.Fill(ds, "students");
            StudentDetails = ds.Tables["students"].DefaultView;
            connection.Close();

        }


        /// <summary>
        /// Method to create new student and creating a new student table if
        /// it doesnt exist in the database
        /// </summary>
        private void CreateStudent()
        {
            if (_student.IsValid)
            {
                string databaseName = "Kwega.db3";
                var connection = new SQLiteConnection("Data Source=" + databaseName + "; Version=3;");
                connection.Open();
                var createStudentTable =
                    "CREATE TABLE IF NOT EXISTS students (student_id INTEGER PRIMARY KEY, first_name TEXT(255), last_name TEXT(255))";

                var createCommand = new SQLiteCommand(createStudentTable, connection);
                createCommand.ExecuteNonQuery();

                string insert_student = "INSERT INTO students(first_name, last_name) VALUES (" +
                                        "'" + _student.FirstName + "', '" + _student.LastName + "')";

                var insert_CMD = new SQLiteCommand(insert_student, connection);
                insert_CMD.ExecuteNonQuery();
                connection.Close();
            }
            else
            {
                MessageBox.Show("Student details weren't saved", "Invalid student!", MessageBoxButton.OK, MessageBoxImage.Information);
            }

        }

        string IDataErrorInfo.Error
        {
            get { return (_student as IDataErrorInfo).Error; }
        }

        string IDataErrorInfo.this[string propertyName]
        {
            get
            {
                string error = (_student as IDataErrorInfo)[propertyName];
                return error;
            }
        }

    }

}

我认为错误可能出在我的 View 模型中，但我最近 3 天无法调用它。下面是我的代码隐藏文件和 xaml 文件。

using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Navigation;
using System.Windows.Shapes;
using WpfApplication_tutorial.Model;
using WpfApplication_tutorial.ViewModel;

namespace WpfApplication_tutorial.UserControls
{
    /// <summary>
    /// Interaction logic for FormOneDataControl.xaml
    /// </summary>
    public partial class FormOneDataControl : UserControl
    {        
        public StudentViewModel ViewModel;

        public FormOneDataControl()
        {
            InitializeComponent();                    
            StudentViewModel studentViewModel = new StudentViewModel();            
            this.DataContext = studentViewModel;
        }  
     }
}          

最后是我的 xaml 文件

<ListView x:Name="FormOneView" ItemsSource="{Binding }" DataContext="{Binding StudentDetails}" >
           <ListView.View>
                                <GridView>
                                    <GridViewColumn Header="First Name" Width="90" DisplayMemberBinding="{Binding Path=FirstName}"  />
                                    <GridViewColumn Header="Last Name" Width="90" DisplayMemberBinding="{Binding Path=LastName}"  />
                                </GridView>
                            </ListView.View>
                        </ListView>

请注意，我尝试使用 ItemsSource="{Binding Path=MethodName}"和 DisplayMemberBinding="{Binding FirstName}"` 例如。

Answer 1

A DataView不是您的数据的好容器。您最好声明一个带有属性的自定义类以显示在您的 ListView 中。这样您就可以使用那些命名属性进行数据绑定(bind)。

目前，您的 XAML 混淆了...您的 ListView正在寻找 StudentDetails项目的属性，即 DataView , 然后你的 GridViewColumn.DisplayMemberBinding s 指向您的 StudentViewModel 中的属性与 DataView 中的项目无关.

相反，使用这些名称属性创建自定义类，然后在您的 StudentViewModel 中创建该类型的集合类和数据绑定(bind)到该集合属性。那么你的GridViewColumn.DisplayMemberBinding应该可以。