[英]Entity Framework Field Is Required (MVVM)
我一直有這個問題,並且在過去的幾天里一直在試圖弄清楚,我設置了第二個測試項目,因為我的第一個項目太大了,無法嘗試解決這個問題。 我對 mvvm 還是很陌生,所以我還在學習。 每當我嘗試使用 Entity 保存字段時,它開始抱怨 FirstName 字段是必需的,我將問題確定為與按鈕的某些內容分開,因為每當我將按鈕移動到與文本框相同的 UserControl 時,它將保存。 MainWindow 中的 TabControl 為每個選項卡都有一個 UserControl,每個選項卡都有自己的 ViewModel,然后 TabControl 本身有一個 ViewModel。
MainWindow只包含按鈕和選項卡控件
<Window.Resources>
<vm:TabControlViewModel x:Key="tab"/>
</Window.Resources>
<Grid DataContext="{StaticResource tab}">
<TabControl Margin="10"
Width="500"
Height="500">
<TabItem Header="Test Tab 1">
<custom:TabOneUserControl/>
</TabItem>
<TabItem Header="Test Tab 2">
<custom:TabTwoUserControl/>
</TabItem>
</TabControl>
<Button Content="Save"
Width="120"
Height="50"
Margin="1114,604,41,38.5"
Command="{Binding SaveCommand}"/>
</Grid>
TabOneUserControl包含文本框和標簽
<UserControl.Resources>
<vm:TabOneUserControlViewModel x:Key="vm"/>
</UserControl.Resources>
<Grid DataContext="{StaticResource vm}">
<StackPanel VerticalAlignment="Center">
<Label Content="First Name"
HorizontalAlignment="Center"/>
<TextBox Width="250"
Height="50"
Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
</Grid>
</UserControl>
TabTwoUserControl包含一個文本框和標簽
<UserControl.Resources>
<vm:TabTwoUserControlViewModel x:Key="vm"/>
</UserControl.Resources>
<Grid DataContext="{StaticResource vm}">
<StackPanel VerticalAlignment="Center">
<Label Content="Last Name"
HorizontalAlignment="Center"/>
<TextBox Width="250"
Height="50"
Text="{Binding LastName, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
</Grid>
</UserControl>
TabControlViewModel為選項卡控件
public class TabControlViewModel
{
public SaveCommand SaveCommand { get; set; }
private TabOneUserControlViewModel tabOneUserControl;
private TabTwoUserControlViewModel tabTwoUserControl;
public TabControlViewModel()
{
tabOneUserControl = new TabOneUserControlViewModel();
tabTwoUserControl = new TabTwoUserControlViewModel();
SaveCommand = new SaveCommand(this);
}
public void SaveInformation()
{
using (TestDbEntities test = new TestDbEntities())
{
test.FNs.Add(new FN
{
FirstName = tabOneUserControl.FirstName
});
test.LNs.Add(new LN
{
LastName = tabTwoUserControl.LastName
});
try
{
test.SaveChanges();
Debug.Print("SAVED CHANGES!");
}
catch (DbEntityValidationException ex)
{
foreach (var validationErrors in ex.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation(
"Class: {0}, Property: {1}, Error: {2}",
validationErrors.Entry.Entity.GetType().FullName,
validationError.PropertyName,
validationError.ErrorMessage);
}
}
}
}
}
}
TabOneUserControlViewModel對於第一個選項卡用戶控件
public class TabOneUserControlViewModel : INotifyPropertyChanged
{
private string firstName;
public event PropertyChangedEventHandler PropertyChanged;
public string FirstName
{
get { return firstName; }
set
{
firstName = value;
OnPropertyChanged("FirstName");
}
}
public TabOneUserControlViewModel()
{
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
TabTwoUserControlViewModel對於第二個選項卡用戶控件
public class TabTwoUserControlViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string lastName;
public string LastName
{
get { return lastName; }
set
{
lastName = value;
OnPropertyChanged("LastName");
}
}
public TabTwoUserControlViewModel()
{
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
感謝評論中的每個人的建議,Nawed 的評論完美地指出了我做錯了什么。 這是我所做的最終代碼更改:
TabControlViewModel去掉了字段,變成了屬性
public class TabControlViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public SaveCommand SaveCommand { get; set; }
public TabOneUserControlViewModel TabOneUserControl { get; set; }
public TabTwoUserControlViewModel TabTwoUserControl { get; set; }
public TabControlViewModel()
{
TabOneUserControl = new TabOneUserControlViewModel();
TabTwoUserControl = new TabTwoUserControlViewModel();
SaveCommand = new SaveCommand(this);
}
public void SaveInformation()
{
using (TestDbEntities test = new TestDbEntities())
{
test.FNs.Add(new FN
{
FirstName = TabOneUserControl.FirstName
});
test.LNs.Add(new LN
{
LastName = TabTwoUserControl.LastName
});
try
{
test.SaveChanges();
Debug.Print("SAVED CHANGES!");
}
catch (DbEntityValidationException ex)
{
foreach (var validationErrors in ex.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation(
"Class: {0}, Property: {1}, Error: {2}",
validationErrors.Entry.Entity.GetType().FullName,
validationError.PropertyName,
validationError.ErrorMessage);
}
}
}
}
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
TabOneUserControl從網格中刪除靜態資源並用常規綁定替換它,然后更改 Text 元素中的綁定,這與我在第二個用戶控件中所做的相同,因此我將否定發布第二個 UserControl:
<Grid DataContext="{Binding TabOneUserControl}">
<StackPanel VerticalAlignment="Center">
<Label Content="First Name"
HorizontalAlignment="Center"/>
<TextBox Width="250"
Height="50"
Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
</Grid>
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