将新数据添加到ObservableCollection并使用MVVM模式绑定到ListView

本文介绍了将新数据添加到ObservableCollection并使用MVVM模式绑定到ListView的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我在使用Wpf应用程序中的ObservableCollection在ListView控件中显示数据时遇到问题。我将2个文本框绑定到PPerson对象（其中包含Fname和LName属性 - 也是未绑定到任何文本框的FullName属性）。当
我将PPerson对象添加到Persons ObservableCollection时，Listview（和observableCollection对象）中的所有Fname和LName列都将更新为2个文本框中的新值。如何使用
新值来阻止先前的行更新？我似乎没有FullName 列的问题 - 只有Fname和LName 列，Fname和LName属性绑定到2个文本框。另外，我在应用启动时在
的构造函数中添加了2个PPersons PersonViewModel。这2个PPersons的Fname和LName没有使用2个文本框中的新值进行更新。

我在下面显示了我的所有代码。我假设每次在文本框中添加新值时都需要创建一个新的PPerson对象，但我该怎么做？

- Person.cs

使用System; 
使用System.Collections.Generic; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks; 
 
 namespace Wpf_tmp.Model 
 {
 public class Person 
 {
 private string fName; 
公共字符串Fname 
 {
 get {return fName; } 
设置
 {
 fName = value; 
} 
} 
 
 private string lName; 
 public string LName 
 {
 get {return lName; } 
设置
 {
 lName = value; 
} 
} 
 
 private string fullName; 
 public string FullName 
 {
 get 
 {
 return fullName = Fname +" " + LName; 
} 
设置
 {
 if（fullName！= value）
 {
 fullName = value; 
} 
} 
} 
} 
}

- PersonViewModel.cs

使用System; 
使用System.Collections.Generic; 
使用System.Collections.ObjectModel; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks; 
使用System.Windows.Input; 
使用Wpf_tmp.Model; 
 
 namespace Wpf_tmp.ViewModel 
 {
 public class PersonViewModel：ObservableObject 
 {
 private Person _person; 
 public person PPerson 
 {
 get 
 {
 return _person; 
} 
设定
 {
 _person = value; 
 // OnPropertyChanged（" Person"）; 
} 
} 
 
 private ObservableCollection< Person> _persons; 
 public ObservableCollection< Person>人
 {
获得
 {
返回_persons; 
} 
设定
 {
 _persons = value; 
 // OnPropertyChanged（" Persons"）; 
} 
} 
 
 private ICommand _submitCommand; 
 public ICommand SubmitCommand 
 {
 get 
 {
 if（_submitCommand == null）
 {
 _submitCommand = new RelayCommand（SubmitExecute，CanSubmitExecute ，假）; 
} 
 return _submitCommand; 
} 
} 
 
 public PersonViewModel（）
 {
 PPerson = new Person（）; 
 Persons = new ObservableCollection< Person>（）{
 new Person {Fname =" joe"，LName =" smith"} 
}; 
人物p =新人{Fname =" steve"，LName =" bank" }; 
 Persons.Add（p）; 
} 
 
 public void SubmitExecute（object parameter）
 {
 Persons.Add（PPerson）; 
 // Person p = new Person（）; 
 //p.Fname = PPerson.Fname; //  - 这些值全部更新整个ListView 
 //p.LName = PPerson.LName; //  - 除了原来的PPersons 
 //Persons.Add(p）; 
} 
 
 private bool CanSubmitExecute（object parameter）
 {
 if（string.IsNullOrEmpty（PPerson.Fname）|| string.IsNullOrEmpty（PPerson.LName）） 
 {
返回true; //  - 这是另一个问题 - 所以我现在设置为true  - 应该是false 
} 
 else 
 {
 return true; 
} 
} 
} 
}

- ObservalbeObject.cs

使用System; 
使用System.Collections.Generic; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks;使用System.ComponentModel 
;使用System.Runtime.CompilerServices 
; 
 
 
名称空间Wpf_tmp 
 {
公共类ObservableObject：INotifyPropertyChanged 
 {
公共事件PropertyChangedEventHandler PropertyChanged; 
 
 public void OnPropertyChanged（string propertyName）
 {
 PropertyChangedEventHandler ph = PropertyChanged; 
 if（ph！= null）
 {
 ph（this，new PropertyChangedEventArgs（propertyName））; 
} 
} 
} 
}

- RelayCommand

 使用System; 
使用System.Collections.Generic; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks; 
使用System.Windows.Input; 
 
名称空间Wpf_tmp 
 {
公共类RelayCommand：ICommand 
 {
 readonly Action< object> _执行; 
 readonly Func< object，bool> _canExecute; 
 bool canExecuteCache; 
 
 public RelayCommand（Action< object> execute，Func< object，bool> canExecute，bool CanExecuteCache）
 {
 _execute = execute; 
 _canExecute = canExecute; 
 canExecuteCache = CanExecuteCache; 
} 
公共事件EventHandler CanExecuteChanged 
 {
 add {CommandManager.RequerySuggested + = value; } 
 remove {CommandManager.RequerySuggested  -  = value; } 
} 
 
 public bool CanExecute（object parameter）
 {
 return _canExecute == null？ true：_canExecute（parameter）; 
} 
 
 public void执行（对象参数）
 {
 _execute（parameter）; 
} 
} 
}

- MainWindow.xaml

< Window x：Class =" Wpf_tmp.MainWindow" 
 xmlns =" http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
 xmlns：x =" http://schemas.microsoft.com/winfx/2006/xaml" 
 xmlns：local =" clr-namespace：Wpf_tmp" 
 xmlns：vm =" clr-namespace：Wpf_tmp.ViewModel" 
 Title =" MainWindow"高度= QUOT; 350"宽度= QUOT; 525"> 
 
< Window.Resources> 
< vm：PersonViewModel x：Key =" pvModel" /> 
< /Window.Resources> 
< Grid DataContext =" {Binding Source = {StaticResource pvModel}}"> 
< Grid.RowDefinitions> 
< RowDefinition Height =" Auto" /> 
< RowDefinition Height =" Auto" /> 
< RowDefinition Height =" Auto" /> 
< RowDefinition Height =" Auto" /> 
< RowDefinition Height =" *" /> 
< /Grid.RowDefinitions> 
< Grid.ColumnDefinitions> 
< ColumnDefinition Width =" Auto" /> 
< ColumnDefinition Width =" *" /> 
< /Grid.ColumnDefinitions> 
< TextBlock Grid.Row =" 0" Grid.Column = QUOT; 0" Text =" First Name"的HorizontalAlignment = QUOT;中心" /> 
< TextBox Grid.Row =" 0" Grid.Column = QUOT 1 QUOT;宽度= QUOT; 100"的HorizontalAlignment = QUOT;中心" Text =" {Binding PPerson.Fname，Mode = TwoWay}" /> 
< TextBlock Grid.Row =" 1" Grid.Column = QUOT; 0" Text =" Last Name"的HorizontalAlignment = QUOT;中心" /> 
< TextBox Grid.Row =" 1" Grid.Column = QUOT 1 QUOT;宽度= QUOT; 100"的HorizontalAlignment = QUOT;中心" Text =" {Binding PPerson.LName，Mode = TwoWay}" /> 
< Button Content ="提交" Command =" {Binding SubmitCommand}"的HorizontalAlignment = QUOT;中心" Grid.Row = QUOT; 2英寸Grid.Column = QUOT; 0" /> 
< ListView ItemsSource =" {Binding Persons}" Grid.Row = QUOT; 3英寸Grid.Column = QUOT 1 QUOT;宽度= QUOT;自动"> 
< ListView.View> 
< GridView> 
< GridViewColumn Header =" First Name" DisplayMemberBinding =" {Binding Fname}"宽度= QUOT;自动" /> 
< GridViewColumn Header =" Last Name" DisplayMemberBinding =" {Binding LName}"宽度= QUOT;自动" /> 
< GridViewColumn Header =" Full Name" DisplayMemberBinding =" {Binding FullName}"宽度= QUOT;自动" /> 
< / GridView> 
< /ListView.View> 
< / ListView> 
< / Grid> 
< / Window>

Rich P

解决方案

I am having a problem displaying data in a ListView control from an ObservableCollection in my Wpf app. I bind 2 textboxes to a PPerson object (which contains Fname and LName properties -- also a FullName property which is not bound to any textbox). When I add the PPerson object to the Persons ObservableCollection all of the Fname and LName columns in the Listview (and observableCollection object) are updated to the new values from the 2 textboxes. How can I prevent the prior rows from updating with the new values? I don't seem to have the problem with the FullName column -- only the Fname and LName columns which the Fname and LName properties are bound to the 2 textboxes. Also, I added 2 PPersons in the constructor of the PersonViewModel on app startup. The Fname and LName of these 2 PPersons does not get updated with the new values from the 2 textboxes.

I show all my code below. I presume that I need to create a new PPerson object each time I add new values in the textboxes, but where do I do this?

--Person.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Wpf_tmp.Model
{
    public class Person
    {
        private string fName;
        public string Fname
        {
            get { return fName; }
            set
            {
                fName = value;
            }
        }

        private string lName;
        public string LName
        {
            get { return lName; }
            set
            {
                lName = value;
            }
        }

        private string fullName;
        public string   FullName
        {
            get
            {
                return fullName = Fname + " " + LName;
            }
            set
            {
                if (fullName != value)
                {
                    fullName = value;
                }
            }
        }
    }
}

--PersonViewModel.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using Wpf_tmp.Model;

namespace Wpf_tmp.ViewModel
{
    public class PersonViewModel : ObservableObject
    {
        private Person _person;
        public Person PPerson
        {
            get
            {
                return _person;
            }
            set
            {
                _person = value;
                //OnPropertyChanged("Person");
            }
        }

        private ObservableCollection<Person> _persons;
        public ObservableCollection<Person> Persons
        {
            get
            {
                return _persons;
            }
            set
            {
                _persons = value;
                //OnPropertyChanged("Persons");
            }
        }

        private ICommand _submitCommand;
        public ICommand SubmitCommand
        {
            get
            {
                if (_submitCommand == null)
                {
                    _submitCommand = new RelayCommand(SubmitExecute, CanSubmitExecute, false);
                }
                return _submitCommand;
            }
        }

        public PersonViewModel()
        {
            PPerson = new Person();
            Persons = new ObservableCollection<Person>(){
                new Person { Fname = "joe", LName = "smith"}
                };
            Person p = new Person { Fname = "steve", LName = "banks" };
            Persons.Add(p);
        }

        public void SubmitExecute(object parameter)
        {
            Persons.Add(PPerson);
            //Person p = new Person();
            //p.Fname = PPerson.Fname;  //--these values all update the entire ListView
            //p.LName = PPerson.LName;  //--except for the original to PPersons
            //Persons.Add(p);
        }

        private bool CanSubmitExecute(object parameter)
        {
            if (string.IsNullOrEmpty(PPerson.Fname) || string.IsNullOrEmpty(PPerson.LName))
            {
                return true;  //--this is another problem -- so I just set to true for now -- should be false
            }
            else
            {
                return true;
            }
        }
    }
}

--ObservalbeObject.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel;
using System.Runtime.CompilerServices;


namespace Wpf_tmp
{
    public class ObservableObject : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler ph = PropertyChanged;
            if (ph != null)
            {
                ph(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

--RelayCommand

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace Wpf_tmp
{
    public class RelayCommand : ICommand
    {
        readonly Action<object> _execute;
        readonly Func<object, bool> _canExecute;
        bool canExecuteCache;

        public RelayCommand(Action<object> execute, Func<object, bool> canExecute, bool CanExecuteCache)
        {
            _execute = execute;
            _canExecute = canExecute;
            canExecuteCache = CanExecuteCache;
        }
        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return _canExecute == null ? true : _canExecute(parameter);
        }

        public void Execute(object parameter)
        {
            _execute(parameter);
        }
    }
}

--MainWindow.xaml

<Window x:Class="Wpf_tmp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:Wpf_tmp"
        xmlns:vm="clr-namespace:Wpf_tmp.ViewModel"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <vm:PersonViewModel x:Key="pvModel" />
    </Window.Resources>
    <Grid DataContext="{Binding Source={StaticResource pvModel}}">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <TextBlock Grid.Row="0" Grid.Column="0" Text="First Name" HorizontalAlignment="Center"/>
        <TextBox Grid.Row="0" Grid.Column="1" Width="100" HorizontalAlignment="Center" Text="{Binding PPerson.Fname, Mode=TwoWay}"/>
        <TextBlock Grid.Row="1" Grid.Column="0" Text="Last Name" HorizontalAlignment="Center"/>
        <TextBox Grid.Row="1" Grid.Column="1" Width="100" HorizontalAlignment="Center" Text="{Binding PPerson.LName, Mode=TwoWay}"/>
        <Button Content="Submit" Command="{Binding SubmitCommand}" HorizontalAlignment="Center" Grid.Row="2" Grid.Column="0"/>
        <ListView ItemsSource="{Binding Persons}" Grid.Row="3" Grid.Column="1" Width="Auto">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="First Name" DisplayMemberBinding="{Binding Fname}" Width="Auto"/>
                    <GridViewColumn Header="Last Name" DisplayMemberBinding="{Binding LName}" Width="Auto"/>
                    <GridViewColumn Header="Full Name" DisplayMemberBinding="{Binding FullName}" Width="Auto"/>
                </GridView>
            </ListView.View>
        </ListView>
    </Grid>
</Window>

Rich P

解决方案

这篇关于将新数据添加到ObservableCollection并使用MVVM模式绑定到ListView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！