Casting Variables / Objects时的RunTime异常
我在VehicleMainModel类中有变量PersonnelName。 我想从PersonnelMainViewModel的对象PersonnelObject获取引用。
运行后，我的代码行抛出Typecast异常：
PersonnelName =（bservableCollection）（PersonnelObject.Select（x =＆gt; x.Name））;
我不明白如何解决这个问题。即使双方都是字符串列表，它不起作用。供你参考，我在这里附上我的两个课程。
请为此提供工作线。
我已经为你截断了不必要的代码。
vehicleMainViewModel
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Seris.Models;
using System.Collections.ObjectModel;
using System.Windows.Input;
using Seris.Commands;
using Seris.ViewModels;
using System.Windows;
using System.Windows.Controls;
using System.Threading;
using System.ComponentModel;
using Seris.Views;
namespace Seris.ViewModels
{
public class VehicleMainViewModel : ObservableObject
{
#region Getters-Setters
//静态变量......
private static VehicleMainViewModel _Instance;
public static VehicleMainViewModel getInstance
{
get
{
if(_Instance==null)
{
_Instance = new VehicleMainViewModel();
}
return _Instance;
}
}
private static AddVehicle _addVehicle;
public static AddVehicle addVehicle
{
get
{
return _addVehicle;
}
set
{
_addVehicle = value;
}
}
//非静态变量......
// Error Components
. . .
private string _PersonnelNameSelected;
public string PersonnelNameSelected
{
get { return _PersonnelNameSelected; }
set
{
if (value == null || (!value.Equals(_PersonnelNameSelected)))
{
_PersonnelNameSelected = value;
EditText = _PersonnelNameSelected;
OnPropertyChanged("PersonnelNameSelected");
validateSpecificData(5);
}
}
}
private ObservableCollection<string> _PersonnelName;
public ObservableCollection<string> PersonnelName
{
get { return _PersonnelName; }
set
{
if (value != _PersonnelName)
{
_PersonnelName = value;
OnPropertyChanged("PersonnelName");
}
}
}
private ObservableCollection<PersonnelModel> _PersonnelObject;
public ObservableCollection<PersonnelModel> PersonnelObject
{
get { return _PersonnelObject; }
set
{
if (value != _PersonnelObject)
{
_PersonnelObject = value;
OnPropertyChanged("PersonnelObject");
}
}
}
private ObservableCollection<VehicleModel> _listItems;
public ObservableCollection<VehicleModel> ListItems
{
get { return _listItems; }
set
{
if (value == null || (!value.Equals(_listItems)))
{
_listItems = value;
}
}
}
// Other Variables
//静态方法......
public static void showMessage(string message)
{
MessageBox.Show(message);
}
//非静态方法......
. . .
public void clearAllData()
{
VehicleNo=null;
Model=null;
ManufacturingDate=null;
IUNo=null;
PersonnelNameSelected=null;
VehicleNo_Error = "";
Model_Error = "";
ManufacturingDate_Error = "";
IUNo_Error = "";
Personnel_Error= "";
}
#endregion
#region Constructors
public VehicleMainViewModel()
{
// Initialization
ListItems = new ObservableCollection<VehicleModel>();
PersonnelObject = PersonnelMainViewModel.getInstance.Personnel_List;
//This line gives error//
PersonnelName = (ObservableCollection<string>) (PersonnelObject.Select(x => x.Name));
// Setting Flags
ErrorMessage = "";
IsEnableReplaceButton = false;
// Commands Initialization
. . .
}
#endregion
}
}
PersonnelMainViewModel
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using System.ComponentModel;
using System.Windows.Markup;
using System.Windows.Data;
using System.Windows.Media.Imaging;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Documents;
using System.Windows.Controls.Primitives;
using System.Windows.Automation.Peers;
using System.Windows.Controls;
using System.Diagnostics;
using System.Security;
using System.Collections.ObjectModel;
using Seris.Models;
using Seris.Views;
using Seris.ViewModels;
using Seris.Properties;
using Seris.Commands;
namespace Seris.ViewModels
{
public class PersonnelMainViewModel :ObservableObject
{
public ObservableCollection<PersonnelModel> Personnel_List;
private ObservableCollection<PersonnelModel> Personnel_copy;
public PersonnelModel model = new PersonnelModel();
public List<string> MyString;
public ICommand EditCommand;
public ICommand AddCommand;
public bool isRemove;
public static ObservableCollection<string> PersonNameList_Updating;
private static PersonnelMainViewModel _Instance;
public static PersonnelMainViewModel getInstance
{
get
{
if (_Instance == null)
{
_Instance = new PersonnelMainViewModel();
}
return _Instance;
}
}
public PersonnelMainViewModel()
{
MyString = new List<string>();
Personnel_copy = new ObservableCollection<PersonnelModel>();
isRemove = false;
Personnel_List = new ObservableCollection<PersonnelModel>
{
new PersonnelModel{ID=Guid.NewGuid(),Name="Mr.Joe",Gender="Male",Hospital="Poly Clinic",EMPID="abc 123",Capabilities="123",Position="Assistant",Title="Test",Status="General",ICNumber="IC 123",Roles="Test"},
new PersonnelModel{ID=Guid.NewGuid(),Name="Su Su",Gender="Female",Hospital="Clementi Clinic",EMPID="abc 1234",Capabilities="1234",Position="Security",Title="Test",Status="General",ICNumber="IC 1234",Roles="Test"},
new PersonnelModel{ID=Guid.NewGuid(),Name="Ms Tan",Gender="Female",Hospital="Bishan Clinic",EMPID="abc 1235",Capabilities="1235",Position="HR",Title="Test",Status="General",ICNumber="IC 1235",Roles="Test"},
};
Personnel_copy = new ObservableCollection<PersonnelModel>
{
new PersonnelModel{ID=Guid.NewGuid(),Name="Mr.Joe",Gender="Male",Hospital="Poly Clinic",EMPID="abc 123",Capabilities="123",Position="Assistant",Title="Test",Status="General",ICNumber="IC 123",Roles="Test"},
new PersonnelModel{ID=Guid.NewGuid(),Name="Su Su",Gender="Female",Hospital="Clementi Clinic",EMPID="abc 1234",Capabilities="1234",Position="Security",Title="Test",Status="General",ICNumber="IC 1234",Roles="Test"},
new PersonnelModel{ID=Guid.NewGuid(),Name="Ms Tan",Gender="Female",Hospital="Bishan Clinic",EMPID="abc 1235",Capabilities="1235",Position="HR",Title="Test",Status="General",ICNumber="IC 1235",Roles="Test"},
};
PersonNameList_Updating = new ObservableCollection<string> (Personnel_List.Select(x => x.Name));
_hos = new ObservableCollection<string> (Personnel_List.Select(x=>x.Hospital) );
EditCommand = new RelayCommand(Edit);
AddCommand = new RelayCommand(Add);
Removecommand = new RelayCommand(Remove);
SearchCommand = new RelayCommand(search);
//string[] textList = this.FindResource("Personnel_vm") as string[];
//ICollectionView view = CollectionViewSource.GetDefaultView(textList);
//new TextSearchFilter(view, this.txtSearch);
}
. . .
#endregion
. . .
}
}
VehicleModel
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.ObjectModel;
using System.Text.RegularExpressions;
using Seris.ViewModels;
namespace Seris.Models
{
public class VehicleModel : ObservableObject
{
#region Getters-Setters
private Guid? _UniqueNo;
public Guid? UniqueNo
{
get { return _UniqueNo; }
set
{
if (value != _UniqueNo)
{
_UniqueNo = value;
OnPropertyChanged("UniqueNo");
}
}
}
private string _VehicleNo;
public string VehicleNo
{
get { return _VehicleNo; }
set
{
if (value != _VehicleNo)
{
_VehicleNo = value.Trim();
OnPropertyChanged("VehicleNo");
}
}
}
private string _Model;
public string Model
{
get { return _Model; }
set
{
if (value != _Model)
{
_Model = value.Trim();
OnPropertyChanged("Model");
}
}
}
private DateTime? _ManufacturingDate;
public DateTime? ManufacturingDate
{
get { return _ManufacturingDate; }
set
{
if (value != _ManufacturingDate)
{
_ManufacturingDate = value;
OnPropertyChanged("ManufacturingDate");
}
}
}
private string _IUNo;
public string IUNo
{
get { return _IUNo; }
set
{
if (value != _IUNo)
{
_IUNo = value.Trim();
OnPropertyChanged("IUNo");
}
}
}
private string _PersonnelNameSelected;
public string PersonnelNameSelected
{
get { return _PersonnelNameSelected; }
set
{
if (value != _PersonnelNameSelected)
{
_PersonnelNameSelected = value;
OnPropertyChanged("PersonnelNameSelected");
}
}
}
#endregion
#region Methods
// Validating Forms
private void ValidateAllData(Object sender)
{
bool errorFlag=false;
if (!Validate_VehicleNo())
{
errorFlag = true;
}
if (!Validate_Model())
{
errorFlag = true;
}
if (!Validate_ManufacturingDate())
{
errorFlag = true;
}
if (!Validate_IUNo())
{
errorFlag = true;
}
if (!Validate_PersonnelName()) // For Future Enhancement
{
errorFlag = true;
}
// Personnel Remaining..........//
if (errorFlag)
throw (new Exception("Invalid Details\nClick on Help for details"));
}
public void ValidateSpecificData(Object sender, int ErrorObj)
{
bool errorFlag = false;
if (sender is VehicleMainViewModel)
{
VehicleMainViewModel senderObject = (VehicleMainViewModel)sender;
errorFlag = false;
switch(ErrorObj)
{
case 1:
if (!Validate_VehicleNo())
{
senderObject.VehicleNo_Error = "3 Caps alphabet following 4 numericals only";
errorFlag = true;
}
else
senderObject.VehicleNo_Error = "";
break;
case 2:
if (!Validate_Model())
{
senderObject.Model_Error = "Mandatory Field";
errorFlag = true;
}
else
senderObject.Model_Error = "";
break;
case 3:
if (!Validate_ManufacturingDate())
{
senderObject.ManufacturingDate_Error = "Can't be blank or future Date";
errorFlag = true;
}
else
senderObject.ManufacturingDate_Error = "";
break;
case 4:
if (!Validate_IUNo())
{
senderObject.IUNo_Error = "10 digits numerical only";
errorFlag = true;
}
else
senderObject.IUNo_Error = "";
break;
case 5:
if (!Validate_PersonnelName())
{
senderObject.Personnel_Error = "Mandatory Fvnield";
errorFlag = true;
}
else
senderObject.Personnel_Error = "";
break;
}
}
}
// To Check Regular Expressions
public bool matchRE(string stringToMatch, string regularExpression)
{
Regex regex = new Regex(@regularExpression);
Match match = regex.Match(stringToMatch);
if (match.Success)
return (true);
else
return (false);
}
#region Validate Methods
public bool Validate_VehicleNo()
{
if (VehicleNo == null || VehicleNo.Trim().Length==0)
return false;
if (matchRE(VehicleNo,"[A-Zz-z][A-Zz-z0-9]{6}"))
return true;
else
return false;
}
public bool Validate_Model()
{
if (Model == null || Model.Trim().Length==0)
return false;
if(Model!=null || Model.Length==0)
return true;
else
return false;
}
public bool Validate_ManufacturingDate()
{
if (ManufacturingDate == null || ManufacturingDate.ToString().Trim().Length == 0)
return false;
if( ManufacturingDate > DateTime.Now )
return false;
return true;
}
public bool Validate_IUNo()
{
if (IUNo == null || IUNo.Trim().Length==0)
return false;
if(matchRE(IUNo,"[0-9]{10}"))
return true;
else
return false;
}
public bool Validate_PersonnelName()
{
if (PersonnelNameSelected == null || PersonnelNameSelected.Trim().Length == 0)
return false;
else
return true;
}
#endregion
#endregion
#region Constructors
public VehicleModel(string VehicleNo, string Model, DateTime? ManufacturingDate, string IUNo, string PersonnelNameSelected)
{
this.UniqueNo = Guid.NewGuid();
this.VehicleNo = VehicleNo;
this.Model = Model;
this.ManufacturingDate = ManufacturingDate;
this.IUNo = IUNo;
this.PersonnelNameSelected = PersonnelNameSelected;
ValidateAllData(this);
}
public VehicleModel()
{
UniqueNo = null;
VehicleNo = null;
Model = null;
ManufacturingDate = null;
IUNo = null;
PersonnelNameSelected = null;
}
#endregion
}
}
AddVehicle.xaml
<Window x:Class="Seris.Views.AddVehicle"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="AddVehicle" Height="650" Width="750"
xmlns:l="clr-namespace:Seris.ViewModels">
<Grid>
<Label Content="Add Vehicle" HorizontalAlignment="Left" Height="27" Margin="261,8,0,0" VerticalAlignment="Top" Width="85" FontWeight="Bold" FontSize="12"/>
<Label Content="SERIS CAD" HorizontalAlignment="Left" Height="30" Margin="61,5,0,0" VerticalAlignment="Top" Width="84" FontWeight="Bold"/>
<Menu x:Name="AddNewPersonnel" HorizontalAlignment="Left" Height="32" Margin="10,32,-329,0" VerticalAlignment="Top" Width="611">
<MenuItem Header="Manage Vehicle >>" Margin="0" />
<MenuItem Header="Add Vehicle >>" Margin="0" />
</Menu>
<GroupBox Header="Vehicle Information" HorizontalAlignment="Left" Height="267" Margin="10,64,0,0" VerticalAlignment="Top" Width="611" FontWeight="Bold" FontSize="12"/>
<Canvas HorizontalAlignment="Left" Height="352" Margin="18,91,0,0" VerticalAlignment="Top" Width="603">
<Label Content="Vehical No" HorizontalAlignment="Left" Height="27" Width="104" Margin="10,10,0,232"/>
<TextBox Name="VehicalNo_Text" Height="27" Width="193" TextWrapping="Wrap" MaxLength="7" Text="{Binding VehicleNo, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Margin="85,10,0,239" />
<Label Name="VehicleNoError_Label" Foreground="Red" Content="{Binding VehicleNo_Error, UpdateSourceTrigger=PropertyChanged}" Height="27" Width="275" Canvas.Left="323" Canvas.Top="10"/>
<Label Content="Model" HorizontalAlignment="Left" Height="27" Width="104" RenderTransformOrigin="0.49,-2.185" Canvas.Left="10" Canvas.Top="62"/>
<TextBox Name="Model_Text" Height="27" Width="193" TextWrapping="Wrap" MaxLength="15" Text="{Binding Model, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Canvas.Left="85" Canvas.Top="62" />
<Label x:Name="ModelError_Label" Foreground="Red" Content="{Binding Model_Error, UpdateSourceTrigger=PropertyChanged}" Height="27" Width="275" Canvas.Left="323" Canvas.Top="62"/>
<Label Content="Manu. Date" HorizontalAlignment="Left" Height="27" Width="104" Canvas.Left="10" Canvas.Top="112"/>
<DatePicker x:Name="ManufacturingDate_DateTime" SelectedDate="{Binding ManufacturingDate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="193" Height="25" Canvas.Left="85" Canvas.Top="114"/>
<Label Name="ManufacturingDateError_Label" Foreground="Red" Content="{Binding ManufacturingDate_Error, UpdateSourceTrigger=PropertyChanged}" Height="27" Width="275" Canvas.Left="323" Canvas.Top="112"/>
<Label Content="IU No" HorizontalAlignment="Left" Height="27" Width="104" Canvas.Left="10" Canvas.Top="157"/>
<TextBox Height="27" Width="193" Name="IUNO_Text" TextWrapping="Wrap" MaxLength="10" Text="{Binding IUNo, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Canvas.Left="85" Canvas.Top="157"/>
<Label Name="IUError_Label" Foreground="Red" Content="{Binding IUNo_Error, UpdateSourceTrigger=PropertyChanged}" Height="27" Width="275" Canvas.Left="323" Canvas.Top="157"/>
<Label Content="Personnel" HorizontalAlignment="Left" Height="27" Width="104" Canvas.Left="10" Canvas.Top="198"/>
<ComboBox x:Name="Personnel_Combo" SelectedValue="{Binding PersonnelNameSelected, UpdateSourceTrigger=PropertyChanged}" ItemsSource="{Binding PersonnelName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Height="27" Width="193" Canvas.Left="85" Canvas.Top="198"/>
<Label Name="Personnel_Label" Foreground="Red" Content="{Binding Personnel_Error, UpdateSourceTrigger=PropertyChanged}" Height="27" Width="275" Canvas.Left="318" Canvas.Top="198"/>
</Canvas>
<Label x:Name="Error_Label" Content="{Binding ErrorMessage, UpdateSourceTrigger=PropertyChanged}" Foreground="Red" HorizontalAlignment="Left" Width="236" Margin="187,345,0,200"/>
<Button Name="Help" Visibility="{Binding HelpVisibility, UpdateSourceTrigger=PropertyChanged}" Command="{Binding OpenHelpWindow_Command}" Height="50" Width="50" Margin="562,377,80,143">
<Button.DataContext>
<l:VehicleHelpViewModel />
</Button.DataContext>
<Image Height="45" Width="45" Source="../Images/help.jpg"/>
</Button>
<Button Name="Save_Button" Command="{Binding SaveButton_Command}" CommandParameter="save" Height="28" Width="81" Content="Save" Margin="265,392,346,150"/>
<TextBlock Name="Preview" Text="{Binding EditText, UpdateSourceTrigger=PropertyChanged}" Margin="13,377,542,168"/>
</Grid>
</Window>
2 个答案:
答案 0 :(得分：1)
您可以通过像这样
初始化来创建ObservableCollectionPersonnelName = new ObservableCollection(PersonnelObject.Select(x => x.Name));
或者
PersonnelName = new ObservableCollection<string>(PersonnelObject.Select(x => x.Name));
答案 1 :(得分：1)
因为Select方法返回IEnumerable<T>，你可能会这样做
IEnumerable<string> personNames = PersonnelObject.Select(x => x.Name);
PersonnelName = new ObservableCollection<string>();// optional if not initialized
foreach(string pName in personNames )
{
PersonnelName.Add(pName);
}
因为Select方法返回一个IEnumerable，它不会传播源集合中所做的更改，你也许可以通过绑定自身解决问题
这是组合框的样本
<ComboBox ItemsSource="{Binding PersonnelObject}"
DisplayMemberPath="Name" />
在上面的示例中，ComboBox在显示PersonnelObject属性时绑定到源集合Name
您可能会将绑定修改为
<ComboBox x:Name="Personnel_Combo"
SelectedValue="{Binding PersonnelNameSelected, UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding PersonnelObject}"
DisplayMemberPath="Name"
SelectedValuePath="Name"
HorizontalAlignment="Left"
Height="27"
Width="193"
Canvas.Left="85"
Canvas.Top="198" />
请注意，我已将ItemsSource更改为绑定到PersonnelObject，并使用SelectedValuePath和DisplayMemberPath属性显示并存储正确的值。
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