MVVM Light:使用数据服务检索数据库项
本文关键字：服务 检索 数据库 数据 Light MVVM | 更新日期: 2023-09-27 18:33:02
我正在做一个示例MVVM Light项目，并正在实现SimpleIoc ViewModelLocator。 我已经能够构建一个IRepositoryService，它从数据库(即公司，员工等(中检索信息并将信息存储到ObservableCollection中。 然后，IRepositoryService 将 ObservableCollection 返回到 ViewModel。 以下是实现方式：
public interface IRepositoryService
{
void GetCompanies(Action<ObservableCollection<Company>, Exception> callback);
void GetEmployees(Action<ObservableCollection<Employee>, Exception> callback);
}
class RepositoryService : IRepositoryService
{
public void GetCompanies(Action<ObservableCollection<Company>, Exception> callback)
{
using (var context = new SidekickEntities())
{
var _companies = from co in context.Companies
select co;
callback(new ObservableCollection<Company>(_companies), null);
}
}
public void GetEmployees(Action<ObservableCollection<Employee>, Exception> callback)
{
using (var context = new SidekickEntities())
{
var _employees = from co in context.Employees
select co;
callback(new ObservableCollection<Employee>(_employees), null);
}
}
}
然后，存储库服务在视图模型中按如下方式使用：
public sealed class CompanyViewModel : ViewModelBase //, IPageViewModel
{
private readonly IRepositoryService _dataService;
private ObservableCollection<Company> _companyList;
/// <summary>
/// Initializes a new instance of the CompanyViewModel class.
/// </summary>
public CompanyViewModel(IRepositoryService dataService)
{
Console.WriteLine("CompanyViewModel DataService Constructor");
try
{
_dataService = dataService;
CompanyList = new ObservableCollection<Company>();
_dataService.GetCompanies(
(companies, error) =>
{
if (error != null)
{
return;
}
CompanyList = companies;
}
);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}
public ObservableCollection<Company> CompanyList
{
get
{
return _companyList;
}
set
{
if (_companyList == value)
{
return;
}
_companyList = value;
RaisePropertyChanged(CompanyListPropertyName);
}
}
}
这一切都很好用，允许我在 DataGrid 中显示数据，但我想知道用于将更改保存回数据库的方法是什么？
例如，如果我将以下内容添加到CompanyViewModelConstructor((的末尾，我将如何将新列表保存回数据库？ 我正在使用实体框架 5.x 访问数据库。
CompanyList.Add(new Company(-1, "Chipotle", "1400 High Street", "", "Columbus", "OH", "43235"));
这是我的一个视图模型的示例
class YearModel : INotifyPropertyChanged
{
#region Members
Year _year;
#endregion
#region Properties
public Year Year
{
get { return _year; }
}
public Int32 id
{
get { return Year.id; }
set
{
Year.id = value;
NotifyPropertyChanged("id");
}
}
public String Code
{
get { return Year.Code; }
set
{
Year.Code = value;
NotifyPropertyChanged("Code");
}
}
public String Description
{
get { return Year.Description; }
set
{
Year.Description = value;
NotifyPropertyChanged("Description");
}
}
public DateTime DateCreated
{
get { return Year.DateCreated; }
set
{
Year.DateCreated = value;
NotifyPropertyChanged("DateCreated");
}
}
public Int32 CreatedByID
{
get { return Year.CreatedByID; }
set
{
Year.CreatedByID = value;
NotifyPropertyChanged("CreatedByID");
}
}
public String CreatedByDesc
{
get { return Year.CreatedByDesc; }
set
{
Year.CreatedByDesc = value;
NotifyPropertyChanged("CreatedByDesc");
}
}
public DateTime DateEdited
{
get { return Year.DateEdited; }
set
{
Year.DateEdited = value;
NotifyPropertyChanged("DateEdited");
}
}
public Int32 EditedByID
{
get { return Year.EditedByID; }
set
{
Year.EditedByID = value;
NotifyPropertyChanged("EditedByID");
}
}
public String EditedByDesc
{
get { return Year.EditedByDesc; }
set
{
Year.EditedByDesc = value;
NotifyPropertyChanged("EditedByDesc");
}
}
#endregion
#region Construction
public YearModel()
{
this._year = new Year
{
id = 0,
Code = "",
Description = "",
DateCreated = new DateTime(1900, 01, 01, 00, 00, 00),
CreatedByID = 0,
CreatedByDesc = "",
DateEdited = new DateTime(1900, 01, 01, 00, 00, 00),
EditedByID = 0,
EditedByDesc = ""
};
}
#endregion
#region Property Change Events
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
#endregion
#region Commands
public ICommand EditCommand
{
get { return new RelayCommand(EditYear); }
}
public ICommand AddCommand
{
get { return new RelayCommand(AddYear); }
}
#endregion
#region Functions
public void EditYear()
{
try
{
Service1Client service = new Service1Client();
Year y = new Year();
y.id = this.id;
y.Code = this.Code;
y.Description = this.Description;
y.DateEdited = DateTime.Now;
y.EditedByID = (Int32)Application.Current.Resources["UserID"];
service.EditYear(y);
MessageBox.Show("Your Year was edited successfully", "Success", MessageBoxButton.OK);
}
catch (Exception ex)
{
logError le = new logError();
le.log(ex, "YearViewModel", "EDIT");
}
}
public void AddYear()
{
try
{
Service1Client service = new Service1Client();
Year y = new Year();
y.Code = this.Code;
y.Description = this.Description;
y.DateCreated = DateTime.Now;
y.CreatedByID = (Int32)Application.Current.Resources["UserID"];
y.DateEdited = this.DateEdited;
service.AddYear(y);
MessageBox.Show("Your new Year was entered successfully", "Success", MessageBoxButton.OK);
}
catch (Exception ex)
{
logError le = new logError();
le.log(ex, "YearViewModel", "ADD");
}
}
#endregion
}
}
<Button Content="Save New"
DataContext="{StaticResource ResourceKey=NewYear}"
Command="{Binding Path=AddCommand}"/>
class RelayCommand : ICommand
{
Action action;
public RelayCommand(Action execute)
{
action = execute;
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
action();
}
}